Re-named the "case" macro to "when".

172 files changed, 1160 insertions, 1156 deletions

diff --git a/stdlib/source/library/lux/meta/code.lux b/stdlib/source/library/lux/meta/code.lux
index 68d5327b1..0bec080e7 100644
--- a/stdlib/source/library/lux/meta/code.lux
+++ b/stdlib/source/library/lux/meta/code.lux
@@ -62,7 +62,7 @@
       (Equivalence Code)
       (implementation
        (def (= x y)
-         (case [x y]
+         (when [x y]
            (,, (with_template [<tag> <eq>]
                  [[[_ {<tag> x'}] [_ {<tag> y'}]]
                   (at <eq> = x' y')]
@@ -88,7 +88,7 @@
 
 (`` (def .public (format ast)
       (-> Code Text)
-      (case ast
+      (when ast
         (,, (with_template [<tag> <struct>]
               [[_ {<tag> value}]
                (at <struct> encoded value)]
@@ -125,7 +125,7 @@
       (-> Code Code Code Code)
       (if (at ..equivalence = original ast)
         substitute
-        (case ast
+        (when ast
           (,, (with_template [<tag>]
                 [[location {<tag> parts}]
                  [location {<tag> (list#each (replaced original substitute) parts)}]]
diff --git a/stdlib/source/library/lux/meta/compiler/default/init.lux b/stdlib/source/library/lux/meta/compiler/default/init.lux
index 019edf1c5..7cf349a43 100644
--- a/stdlib/source/library/lux/meta/compiler/default/init.lux
+++ b/stdlib/source/library/lux/meta/compiler/default/init.lux
@@ -103,7 +103,7 @@
 (def (read source reader)
   (-> Source Reader (///analysis.Operation [Source Code]))
   (function (_ [bundle compiler])
-    (case (reader source)
+    (when (reader source)
       {.#Left [source' error]}
       {try.#Failure error}
 
@@ -211,7 +211,7 @@
     [reader (///declaration.lifted_analysis
              (..reader module aliases source))]
     (function (_ state)
-      (case (///phase.result' state (..iteration' wrapper archive expander reader source pre_payload))
+      (when (///phase.result' state (..iteration' wrapper archive expander reader source pre_payload))
         {try.#Success [state source&requirements&buffer]}
         {try.#Success [state {.#Some source&requirements&buffer}]}
 
@@ -266,14 +266,14 @@
                                                         (..iteration wrapper archive expander module source buffer ///syntax.no_aliases))])
                               (do !
                                 [[state ?source&requirements&temporary_payload] iteration]
-                                (case ?source&requirements&temporary_payload
+                                (when ?source&requirements&temporary_payload
                                   {.#None}
                                   (do !
                                     [[state [analysis_module [final_buffer final_registry]]]
                                      (<| (///phase.result' state)
                                          (do [! ///phase.monad]
                                            [_ (if (text#= program_module module)
-                                                (case program_definition
+                                                (when program_definition
                                                   {.#Some program_definition}
                                                   (///declaration.lifted_generation
                                                    (define_program! archive program global program_module program_definition))
diff --git a/stdlib/source/library/lux/meta/compiler/default/platform.lux b/stdlib/source/library/lux/meta/compiler/default/platform.lux
index b0ce99018..12b6c63f1 100644
--- a/stdlib/source/library/lux/meta/compiler/default/platform.lux
+++ b/stdlib/source/library/lux/meta/compiler/default/platform.lux
@@ -426,7 +426,7 @@
       (monad.mix try.monad
                  (function (_ [extension expected] output)
                    (with_expansions [<inherited> (dictionary.has extension expected output)]
-                     (case (dictionary.value extension output)
+                     (when (dictionary.value extension output)
                        {.#None}
                        {try.#Success <inherited>}
                        
@@ -519,7 +519,7 @@
                                                          (do !
                                                            [[_ dependence] (stm.update (..depend importer module) dependence)]
                                                            (in dependence)))]
-                                           (case (..verify_dependencies importer module dependence)
+                                           (when (..verify_dependencies importer module dependence)
                                              {try.#Failure error}
                                              (in [(async.resolved {try.#Failure error})
                                                   {.#None}])
@@ -532,13 +532,13 @@
                                                       {.#None}])
                                                  (do !
                                                    [@pending (stm.read pending)]
-                                                   (case (dictionary.value module @pending)
+                                                   (when (dictionary.value module @pending)
                                                      {.#Some [return signal]}
                                                      (in [return
                                                           {.#None}])
                                                      
                                                      {.#None}
-                                                     (case (if (archive.reserved? archive module)
+                                                     (when (if (archive.reserved? archive module)
                                                              (do try.monad
                                                                [@module (archive.id module archive)]
                                                                (in [@module archive]))
@@ -560,14 +560,14 @@
                                                        {try.#Failure error}
                                                        (in [(async#in {try.#Failure error})
                                                             {.#None}]))))))))))))
-                 _ (case signal
+                 _ (when signal
                      {.#None}
                      (in [])
                      
                      {.#Some [context @module resolver]}
                      (do !
                        [result (compile customs importer import! @module context module)
-                        result (case result
+                        result (when result
                                  {try.#Failure error}
                                  (in result)
 
@@ -652,7 +652,7 @@
         (do [! (try.with async.monad)]
           []
           (if (set.empty? duplicates)
-            (case new_dependencies
+            (when new_dependencies
               {.#End}
               (in [archive (list)])
 
@@ -672,7 +672,7 @@
           (-> (List ///.Custom) Lux_Importer descriptor.Module (Set descriptor.Module) (List descriptor.Module) Lux_Context Lux_Return))
         (do (try.with async.monad)
           [[archive state/*] (any|after_imports customs import! module duplicates new_dependencies archive)]
-          (in [archive (case state/*
+          (in [archive (when state/*
                          {.#End}
                          state
 
@@ -717,9 +717,9 @@
               [.let [new_dependencies (the ///.#dependencies compilation)
                      [all_dependencies duplicates] (with_new_dependencies new_dependencies all_dependencies)]
                [archive _] (any|after_imports customs import! module duplicates new_dependencies archive)]
-              (case ((the ///.#process compilation) state archive)
+              (when ((the ///.#process compilation) state archive)
                 {try.#Success [state more|done]}
-                (case more|done
+                (when more|done
                   {.#Left more}
                   (let [continue! (sharing [state document object]
                                     (is (///.Compilation state document object)
@@ -756,9 +756,9 @@
               [.let [new_dependencies (the ///.#dependencies compilation)
                      [all_dependencies duplicates] (with_new_dependencies new_dependencies all_dependencies)]
                [archive state] (lux|after_imports customs import! module duplicates new_dependencies [archive state])]
-              (case (next_compilation module [archive state] compilation)
+              (when (next_compilation module [archive state] compilation)
                 {try.#Success [state more|done]}
-                (case more|done
+                (when more|done
                   {.#Left more}
                   (let [continue! (sharing [<type_vars>]
                                     (is <Platform>
@@ -773,7 +773,7 @@
                     [_ (let [report (..module_compilation_log module state)]
                          (with_expansions [<else> (in (debug.log! report))]
                            (for @.js (is (Async (Try Any))
-                                         (case console.default
+                                         (when console.default
                                            {.#None}
                                            <else>
                                            
@@ -820,13 +820,13 @@
             (loop (again [customs (for @.old (as (List (///.Custom Fake_State Fake_Document Fake_Object))
                                                  all_customs)
                                        all_customs)])
-              (case customs
+              (when customs
                 {.#End}
                 ((..lux_compiler import context platform compilation_sources compiler (compiler input))
                  all_customs importer import! @module [archive lux_state] module)
                 
                 {.#Item [custom_state custom_key custom_format custom_parser custom_compiler] tail}
-                (case (custom_compiler input)
+                (when (custom_compiler input)
                   {try.#Failure _}
                   (again tail)
                   
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/analysis.lux b/stdlib/source/library/lux/meta/compiler/language/lux/analysis.lux
index 4a1b68582..7df0d6232 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/analysis.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/analysis.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except Tuple Variant Pattern nat int rev case local except)
+  [lux (.except Tuple Variant Pattern nat int rev when local except)
    [abstract
     [equivalence (.only Equivalence)]
     [hash (.only Hash)]
@@ -61,7 +61,7 @@
      {#Simple Simple}
      {#Structure (Complex Analysis)}
      {#Reference Reference}
-     {#Case Analysis (Match' Analysis)}
+     {#When Analysis (Match' Analysis)}
      {#Function (Environment Analysis) Analysis}
      {#Apply Analysis Analysis}
      {#Extension (Extension Analysis)})))
@@ -83,7 +83,7 @@
   (Equivalence Analysis)
   (implementation
    (def (= reference sample)
-     (.case [reference sample]
+     (.when [reference sample]
        [{#Simple reference} {#Simple sample}]
        (at /simple.equivalence = reference sample)
 
@@ -93,8 +93,8 @@
        [{#Reference reference} {#Reference sample}]
        (at reference.equivalence = reference sample)
 
-       [{#Case [reference_analysis reference_match]}
-        {#Case [sample_analysis sample_match]}]
+       [{#When [reference_analysis reference_match]}
+        {#When [sample_analysis sample_match]}]
        (and (= reference_analysis sample_analysis)
             (at (list.equivalence (branch_equivalence =)) = {.#Item reference_match} {.#Item sample_match}))
 
@@ -119,7 +119,7 @@
      (template (<name> content)
        [{<tag> content}]))]
 
-  [case ..#Case]
+  [when ..#When]
   )
 
 (def .public unit
@@ -166,7 +166,7 @@
   (loop (again [abstraction analysis
                 inputs (is (List Analysis)
                            (list))])
-    (.case abstraction
+    (.when abstraction
       {#Apply input next}
       (again next {.#Item input inputs})
 
@@ -200,7 +200,7 @@
 
 (def .public (format analysis)
   (Format Analysis)
-  (.case analysis
+  (.when analysis
     {#Simple it}
     (/simple.format it)
     
@@ -210,7 +210,7 @@
     {#Reference reference}
     (reference.format reference)
     
-    {#Case analysis match}
+    {#When analysis match}
     (%.format "({"
               (|> {.#Item match}
                   (list#each (function (_ [when then])
@@ -259,7 +259,7 @@
   (All (_ a) (-> Source (Operation a) (Operation a)))
   (function (_ [bundle state])
     (let [old_source (the .#source state)]
-      (.case (action [bundle (has .#source source state)])
+      (.when (action [bundle (has .#source source state)])
         {try.#Success [[bundle' state'] output]}
         {try.#Success [[bundle' (has .#source old_source state')]
                        output]}
@@ -279,7 +279,7 @@
     action
     (function (_ [bundle state])
       (let [old_location (the .#location state)]
-        (.case (action [bundle (has .#location location state)])
+        (.when (action [bundle (has .#location location state)])
           {try.#Success [[bundle' state'] output]}
           {try.#Success [[bundle' (has .#location old_location state')]
                          output]}
@@ -300,7 +300,7 @@
 (def .public (of_try it)
   (All (_ a) (-> (Try a) (Operation a)))
   (function (_ [bundle state])
-    (.case it
+    (.when it
       {try.#Failure error}
       {try.#Failure (located (the .#location state) error)}
 
@@ -320,7 +320,7 @@
 (def .public (with_exception exception message action)
   (All (_ e o) (-> (Exception e) e (Operation o) (Operation o)))
   (function (_ bundle,state)
-    (.case (exception.with exception message
+    (.when (exception.with exception message
              (action bundle,state))
       {try.#Failure error}
       (let [[bundle state] bundle,state]
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/complex.lux b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/complex.lux
index 0d00367b9..40d90f729 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/complex.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/complex.lux
@@ -53,7 +53,7 @@
   (All (_ a) (-> (Equivalence a) (Equivalence (Complex a))))
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        [{#Variant [reference_lefts reference_right? reference_value]}
         {#Variant [sample_lefts sample_right? sample_value]}]
        (and (n.= reference_lefts sample_lefts)
@@ -73,7 +73,7 @@
      (..equivalence (at super equivalence)))
    
    (def (hash value)
-     (case value
+     (when value
        {#Variant [lefts right? value]}
        (all n.* 2
             (at n.hash hash lefts)
@@ -87,7 +87,7 @@
 
 (def .public (format %it it)
   (All (_ a) (-> (Format a) (Format (Complex a))))
-  (case it
+  (when it
     {#Variant [lefts right? it]}
     (%.format "{" (%.nat lefts) " " (%.bit right?) " " (%it it) "}")
     
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/coverage.lux b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/coverage.lux
index 45097d4a5..3403461fb 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/coverage.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/coverage.lux
@@ -73,7 +73,7 @@
 
 (def (alternatives coverage)
   (-> Coverage (List Coverage))
-  (case coverage
+  (when coverage
     {#Alt left right}
     (list.partial left (alternatives right))
 
@@ -84,7 +84,7 @@
   (Equivalence Coverage)
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        [{#Exhaustive} {#Exhaustive}]
        true
 
@@ -123,7 +123,7 @@
 
 (def .public (format value)
   (%.Format Coverage)
-  (case value
+  (when value
     {#Bit it}
     (%.bit it)
 
@@ -165,7 +165,7 @@
 
 (def .public (coverage pattern)
   (-> Pattern (Try Coverage))
-  (case pattern
+  (when pattern
     (^.or {//pattern.#Simple {//simple.#Unit}}
           {//pattern.#Bind _})
     {try.#Success {#Exhaustive}}
@@ -190,7 +190,7 @@
     ... Tuple patterns can be exhaustive if there is exhaustiveness for all of
     ... their sub-patterns.
     {//pattern.#Complex {//complex.#Tuple membersP+}}
-    (case (list.reversed membersP+)
+    (when (list.reversed membersP+)
       (^.or (list)
             (list _))
       (exception.except ..invalid_tuple [(list.size membersP+)])
@@ -202,7 +202,7 @@
                    (function (_ leftP rightC)
                      (do !
                        [leftC (coverage leftP)]
-                       (case rightC
+                       (when rightC
                          {#Exhaustive}
                          (in leftC)
 
@@ -249,7 +249,7 @@
 
 (def .public (exhaustive? coverage)
   (-> Coverage Bit)
-  (case coverage
+  (when coverage
     {#Exhaustive}
     true
 
@@ -269,7 +269,7 @@
                                   <redundancy>
                                   ... There are now 2 alternative paths.
                                   <alternatively>)]
-    (case [addition so_far]
+    (when [addition so_far]
       ... 2 bit coverages are exhaustive if they complement one another.
       [{#Bit sideA} {#Bit sideSF}]
       (if (xor sideA sideSF)
@@ -307,7 +307,7 @@
               (do [! try.monad]
                 [casesM (monad.mix !
                                    (function (_ [tagA coverageA] casesSF')
-                                     (case (dictionary.value tagA casesSF')
+                                     (when (dictionary.value tagA casesSF')
                                        {.#Some coverageSF}
                                        (do !
                                          [coverageM (composite coverageA coverageSF)]
@@ -324,7 +324,7 @@
                       {#Variant (maybe#composite allA allSF) casesM})))))
 
       [{#Seq leftA rightA} {#Seq leftSF rightSF}]
-      (case [(/#= leftSF leftA) (/#= rightSF rightA)]
+      (when [(/#= leftSF leftA) (/#= rightSF rightA)]
         ... Same prefix
         [.true .false]
         (do try.monad
@@ -374,14 +374,14 @@
                                        (List Coverage)]))
                              (function (_ coverageA possibilitiesSF)
                                (loop (again [altsSF possibilitiesSF])
-                                 (case altsSF
+                                 (when altsSF
                                    {.#End}
                                    (in [{.#None} (list coverageA)])
                                    
                                    {.#Item altSF altsSF'}
                                    (do !
                                      [altMSF (composite coverageA altSF)]
-                                     (case altMSF
+                                     (when altMSF
                                        {#Alt _}
                                        (do !
                                          [[success altsSF+] (again altsSF')]
@@ -393,12 +393,12 @@
                       possibilitiesSF (alternatives so_far)])
           (do !
             [[addition' possibilitiesSF'] (fuse_once addition possibilitiesSF)]
-            (case addition'
+            (when addition'
               {.#Some addition'}
               (again addition' possibilitiesSF')
               
               {.#None}
-              (case (list.reversed possibilitiesSF')
+              (when (list.reversed possibilitiesSF')
                 {.#Item last prevs}
                 (in (list#mix (function (_ left right) {#Alt left right})
                               last
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/inference.lux b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/inference.lux
index 5bbf38167..d85a576cd 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/inference.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/inference.lux
@@ -56,7 +56,7 @@
 
 (def .public (quantified @var @parameter :it:)
   (-> check.Var Nat Type Type)
-  (case :it:
+  (when :it:
     {.#Primitive name co_variant}
     {.#Primitive name (list#each (quantified @var @parameter) co_variant)}
 
@@ -95,7 +95,7 @@
 ... as a function type, this method of inference should work.
 (def (general' vars archive analyse inferT args)
   (-> (List check.Var) Archive Phase Type (List Code) (Operation [Type_Context (List check.Var) Type (List Analysis)]))
-  (case args
+  (when args
     {.#End}
     (do phase.monad
       [just_before (/type.check check.context)
@@ -103,7 +103,7 @@
       (in [just_before vars inferT (list)]))
     
     {.#Item argC args'}
-    (case inferT
+    (when inferT
       {.#Named name unnamedT}
       (general' vars archive analyse unnamedT args)
 
@@ -118,7 +118,7 @@
         (general' vars archive analyse (maybe.trusted (type.applied (list :ex:) inferT)) args))
 
       {.#Apply inputT transT}
-      (case (type.applied (list inputT) transT)
+      (when (type.applied (list inputT) transT)
         {.#Some outputT}
         (general' vars archive analyse outputT args)
 
@@ -143,7 +143,7 @@
       {.#Var infer_id}
       (do phase.monad
         [?inferT' (/type.check (check.peek infer_id))]
-        (case ?inferT'
+        (when ?inferT'
           {.#Some inferT'}
           (general' vars archive analyse inferT' args)
 
@@ -159,7 +159,7 @@
   (do [! phase.monad]
     [[just_before vars :inference: terms] (general' (list) archive analyse inferT args)]
     (in [:inference: terms])
-    ... (case vars
+    ... (when vars
     ...   (list)
     ...   (in [:inference: terms])
 
@@ -170,7 +170,7 @@
     ...                     [quantifications (monad.mix ! (function (_ @var level)
     ...                                                     (do !
     ...                                                       [:var: (check.try (check.identity vars @var))]
-    ...                                                       (case :var:
+    ...                                                       (when :var:
     ...                                                         {try.#Success _}
     ...                                                         (in level)
 
@@ -191,7 +191,7 @@
 (def (with_recursion @self recursion)
   (-> Nat Type Type Type)
   (function (again it)
-    (case it
+    (when it
       (^.or {.#Parameter index}
             {.#Apply {.#Primitive "" {.#End}}
                      {.#Parameter index}})
@@ -227,7 +227,7 @@
          (-> (,, (template.spliced <types>)) Type (Operation Type))
          (loop (again [depth 0
                        it complex])
-           (case it
+           (when it
              {.#Named name it}
              (again depth it)
 
@@ -239,7 +239,7 @@
               [.#ExQ])
 
              {.#Apply parameter abstraction}
-             (case (type.applied (list parameter) abstraction)
+             (when (type.applied (list parameter) abstraction)
                {.#Some it}
                (again depth it)
 
@@ -266,7 +266,7 @@
    (|> it
        type.flat_variant
        (list.after lefts)
-       (pipe.case
+       (pipe.when
          {.#Item [head tail]}
          (let [case (if right?
                       (type.variant tail)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/macro.lux b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/macro.lux
index cf6ede122..b8bf793ec 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/macro.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/macro.lux
@@ -37,7 +37,7 @@
   (function (_ state)
     (do try.monad
       [output (expander macro inputs state)]
-      (case output
+      (when output
         {try.#Failure error}
         ((meta.failure (exception.error ..expansion_failed [name inputs error])) state)
 
@@ -48,7 +48,7 @@
   (-> Expander Symbol Macro (List Code) (Meta Code))
   (do meta.monad
     [expansion (..expansion expander name macro inputs)]
-    (case expansion
+    (when expansion
       (list single)
       (in single)
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/module.lux b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/module.lux
index 8284b0301..b7a808dbf 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/module.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/module.lux
@@ -43,7 +43,7 @@
                                                   already_existing Global])
   (exception.report
    (list ["Definition" (%.symbol name)]
-         ["Original" (case already_existing
+         ["Original" (when already_existing
                        {.#Alias alias}
                        (format "alias " (%.symbol alias))
                        
@@ -63,7 +63,7 @@
                                                             state Module_State])
   (exception.report
    (list ["Module" module]
-         ["Desired state" (case state
+         ["Desired state" (when state
                             {.#Active}   "Active"
                             {.#Compiled} "Compiled"
                             {.#Cached}   "Cached")])))
@@ -110,7 +110,7 @@
      (|> state
          (the .#modules)
          (property.value module)
-         (pipe.case
+         (pipe.when
            {.#Some _}
            true
            
@@ -126,7 +126,7 @@
      [self_name meta.current_module_name
       self meta.current_module]
      (function (_ state)
-       (case (property.value name (the .#definitions self))
+       (when (property.value name (the .#definitions self))
          {.#None}
          {try.#Success [(revised .#modules
                                  (property.has self_name
@@ -164,9 +164,9 @@
      (-> Text (Operation Any))
      (///extension.lifted
       (function (_ state)
-        (case (|> state (the .#modules) (property.value module_name))
+        (when (|> state (the .#modules) (property.value module_name))
           {.#Some module}
-          (let [active? (case (the .#module_state module)
+          (let [active? (when (the .#module_state module)
                           {.#Active}
                           true
                           
@@ -188,10 +188,10 @@
      (-> Text (Operation Bit))
      (///extension.lifted
       (function (_ state)
-        (case (|> state (the .#modules) (property.value module_name))
+        (when (|> state (the .#modules) (property.value module_name))
           {.#Some module}
           {try.#Success [state
-                         (case (the .#module_state module)
+                         (when (the .#module_state module)
                            {<tag>}
                            true
                            
@@ -211,7 +211,7 @@
   (-> Bit (List Label) Bit Type (Operation Any))
   (do [! ///.monad]
     [self_name (///extension.lifted meta.current_module_name)
-     [type_module type_name] (case type
+     [type_module type_name] (when type
                                {.#Named type_name _}
                                (in type_name)
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/pattern.lux b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/pattern.lux
index daf608222..836c7c30d 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/pattern.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/pattern.lux
@@ -27,7 +27,7 @@
   (Equivalence Pattern)
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        [{#Simple reference} {#Simple sample}]
        (at //simple.equivalence = reference sample)
        
@@ -42,7 +42,7 @@
 
 (def .public (format it)
   (%.Format Pattern)
-  (case it
+  (when it
     {#Simple it}
     (//simple.format it)
     
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/scope.lux b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/scope.lux
index 538874881..c7d17b9cb 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/scope.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/scope.lux
@@ -52,7 +52,7 @@
   (-> Text Scope (Maybe [Type Variable]))
   (loop (again [idx 0
                 mappings (the [.#captured .#mappings] scope)])
-    (case mappings
+    (when mappings
       {.#Item [_name [_source_type _source_ref]] mappings'}
       (if (text#= name _name)
         {.#Some [_source_type {variable.#Foreign idx}]}
@@ -68,7 +68,7 @@
 
 (def (reference name scope)
   (-> Text Scope (Maybe [Type Variable]))
-  (case (..local name scope)
+  (when (..local name scope)
     {.#Some type}
     {.#Some type}
 
@@ -82,7 +82,7 @@
      (let [[inner outer] (|> state
                              (the .#scopes)
                              (list.split_when (|>> (reference? name))))]
-       (case outer
+       (when outer
          {.#End}
          {.#Right [state {.#None}]}
 
@@ -111,7 +111,7 @@
 (def .public (with_local [name type] action)
   (All (_ a) (-> [Text Type] (Operation a) (Operation a)))
   (function (_ [bundle state])
-    (case (the .#scopes state)
+    (when (the .#scopes state)
       {.#Item head tail}
       (let [old_mappings (the [.#locals .#mappings] head)
             new_var_id (the [.#locals .#counter] head)
@@ -120,10 +120,10 @@
                                   (|>> (revised .#counter ++)
                                        (revised .#mappings (property.has name [type new_var_id]))))
                               head)]
-        (case (phase.result' [bundle (has .#scopes {.#Item new_head tail} state)]
+        (when (phase.result' [bundle (has .#scopes {.#Item new_head tail} state)]
                              action)
           {try.#Success [[bundle' state'] output]}
-          (case (the .#scopes state')
+          (when (the .#scopes state')
             {.#Item head' tail'}
             (let [scopes' {.#Item (has .#locals (the .#locals head) head')
                                   tail'}]
@@ -152,7 +152,7 @@
 (def .public (reset action)
   (All (_ a) (-> (Operation a) (Operation a)))
   (function (_ [bundle state])
-    (case (action [bundle (has .#scopes (list ..empty) state)])
+    (when (action [bundle (has .#scopes (list ..empty) state)])
       {try.#Success [[bundle' state'] output]}
       {try.#Success [[bundle' (has .#scopes (the .#scopes state) state')]
                      output]}
@@ -163,9 +163,9 @@
 (def .public (with action)
   (All (_ a) (-> (Operation a) (Operation [Scope a])))
   (function (_ [bundle state])
-    (case (action [bundle (revised .#scopes (|>> {.#Item ..empty}) state)])
+    (when (action [bundle (revised .#scopes (|>> {.#Item ..empty}) state)])
       {try.#Success [[bundle' state'] output]}
-      (case (the .#scopes state')
+      (when (the .#scopes state')
         {.#Item head tail}
         {try.#Success [[bundle' (has .#scopes tail state')]
                        [head output]]}
@@ -180,7 +180,7 @@
   (Operation Register)
   (extension.lifted
    (function (_ state)
-     (case (the .#scopes state)
+     (when (the .#scopes state)
        {.#Item top _}
        {try.#Success [state (the [.#locals .#counter] top)]}
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/simple.lux b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/simple.lux
index 4b092ad00..239bb848c 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/simple.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/simple.lux
@@ -31,7 +31,7 @@
   (Equivalence Simple)
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        [{#Unit} {#Unit}]
        true
        
@@ -50,7 +50,7 @@
 
 (def .public (format it)
   (Format Simple)
-  (case it
+  (when it
     {#Unit}
     "[]"
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/type.lux b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/type.lux
index b534b616a..85f275a67 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/analysis/type.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/analysis/type.lux
@@ -29,7 +29,7 @@
 (def .public (check action)
   (All (_ a) (-> (Check a) (Operation a)))
   (function (_ (^.let stateE [bundle state]))
-    (case (action (the .#type_context state))
+    (when (action (the .#type_context state))
       {try.#Success [context' output]}
       {try.#Success [[bundle (has .#type_context context' state)]
                      output]}
@@ -42,7 +42,7 @@
 
 (def .public (existential? type)
   (-> Type Bit)
-  (case type
+  (when type
     {.#Primitive actual {.#End}}
     (text.starts_with? ..prefix actual)
 
@@ -95,7 +95,7 @@
              ...        _ (monad.each ! (function (_ @new)
              ...                          (do !
              ...                            [:new: (check.try (check.identity new_vars @new))]
-             ...                            (case :new:
+             ...                            (when :new:
              ...                              {try.#Success :new:}
              ...                              (in :new:)
              
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/generation.lux b/stdlib/source/library/lux/meta/compiler/language/lux/generation.lux
index 2e1252dec..1b9dbb961 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/generation.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/generation.lux
@@ -125,7 +125,7 @@
      (All (_ anchor expression declaration output) <with_type>)
      (function (_ body)
        (function (_ [bundle state])
-         (case (body [bundle (has <tag> {.#Some <with_value>} state)])
+         (when (body [bundle (has <tag> {.#Some <with_value>} state)])
            {try.#Success [[bundle' state'] output]}
            {try.#Success [[bundle' (has <tag> (the <tag> state) state')]
                           output]}
@@ -137,7 +137,7 @@
      (All (_ anchor expression declaration)
        (Operation anchor expression declaration <get_type>))
      (function (_ (^.let stateE [bundle state]))
-       (case (the <tag> state)
+       (when (the <tag> state)
          {.#Some output}
          {try.#Success [stateE output]}
 
@@ -206,7 +206,7 @@
   (All (_ anchor expression declaration)
     (-> unit.ID [(Maybe unit.ID) expression] (Operation anchor expression declaration Any)))
   (function (_ (^.let state+ [bundle state]))
-    (case (at (the #host state) evaluate label code)
+    (when (at (the #host state) evaluate label code)
       {try.#Success output}
       {try.#Success [state+ output]}
 
@@ -217,7 +217,7 @@
   (All (_ anchor expression declaration)
     (-> declaration (Operation anchor expression declaration Any)))
   (function (_ (^.let state+ [bundle state]))
-    (case (at (the #host state) execute code)
+    (when (at (the #host state) execute code)
       {try.#Success output}
       {try.#Success [state+ output]}
 
@@ -228,7 +228,7 @@
   (All (_ anchor expression declaration)
     (-> unit.ID (Maybe Text) [(Maybe unit.ID) expression] (Operation anchor expression declaration [Text Any declaration])))
   (function (_ (^.let stateE [bundle state]))
-    (case (at (the #host state) define context custom code)
+    (when (at (the #host state) define context custom code)
       {try.#Success output}
       {try.#Success [stateE output]}
 
@@ -240,7 +240,7 @@
     (-> artifact.ID (Maybe Text) declaration (Operation anchor expression declaration Any)))
   (do [! phase.monad]
     [?buffer (extension.read (the #buffer))]
-    (case ?buffer
+    (when ?buffer
       {.#Some buffer}
       ... TODO: Optimize by no longer checking for overwrites...
       (if (sequence.any? (|>> product.left (n.= artifact_id)) buffer)
@@ -286,7 +286,7 @@
                     (do try.monad
                       [[_module output registry] (archive.find _module archive)]
                       {try.#Success registry}))]
-        (case (registry.id _name registry)
+        (when (registry.id _name registry)
           {.#None}
           (exception.except ..unknown_definition [name (registry.definitions registry)])
           
@@ -305,7 +305,7 @@
                     (do try.monad
                       [[_module output registry] (archive.find _module archive)]
                       {try.#Success registry}))]
-        (case (registry.find_definition _name registry)
+        (when (registry.find_definition _name registry)
           {.#None}
           (exception.except ..unknown_definition [name (registry.definitions registry)])
           
@@ -326,7 +326,7 @@
   (All (_ anchor expression declaration)
     (-> Archive (Operation anchor expression declaration unit.ID)))
   (function (_ (^.let stateE [bundle state]))
-    (case (the #context state)
+    (when (the #context state)
       {.#None}
       (exception.except ..no_context [])
       
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis.lux
index a65940d6b..9ea79eab0 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis.lux
@@ -22,7 +22,7 @@
   ["[1][0]" simple]
   ["[1][0]" complex]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" function]
   ["/[1]" //
    ["[1][0]" extension]
@@ -43,7 +43,7 @@
 (def variant_analysis
   (template (_ analysis archive tag values)
     ... (-> Phase Archive Symbol (List Code) (Operation Analysis))
-    [(case values
+    [(when values
        (list value)
        (/complex.variant analysis tag archive value)
 
@@ -53,19 +53,19 @@
 (def sum_analysis
   (template (_ analysis archive lefts right? values)
     ... (-> Phase Archive Nat Bit (List Code) (Operation Analysis))
-    [(case values
+    [(when values
        (list value)
        (/complex.sum analysis lefts right? archive value)
 
        _
        (/complex.sum analysis lefts right? archive (code.tuple values)))]))
 
-(def case_analysis
+(def when_analysis
   (template (_ analysis archive input branches code)
     ... (-> Phase Archive Code (List Code) Code (Operation Analysis))
-    [(case (list.pairs branches)
+    [(when (list.pairs branches)
        {.#Some branches}
-       (/case.case analysis branches archive input)
+       (/when.when analysis branches archive input)
 
        {.#None}
        (//.except ..invalid [code]))]))
@@ -76,11 +76,11 @@
     [(do [! //.monad]
        [[functionT functionA] (/type.inferring
                                (analysis archive functionC))]
-       (case functionA
+       (when functionA
          (/.constant def_name)
          (do !
            [?macro (//extension.lifted (meta.macro def_name))]
-           (case ?macro
+           (when ?macro
              {.#Some macro}
              (do !
                [expansion (//extension.lifted (/macro.single_expansion expander def_name macro argsC+))]
@@ -99,7 +99,7 @@
         ... The location must be set in the state for the sake
         ... of having useful error messages.
         (/.with_location location)
-        (case code
+        (when code
           (^.with_template [<tag> <analyser>]
             [[_ {<tag> value}]
              (<analyser> value)])
@@ -120,7 +120,7 @@
           (..variant_analysis analysis archive tag values)
 
           (^.` ({(^.,* branches)} (^., input)))
-          (..case_analysis analysis archive input branches code)
+          (..when_analysis analysis archive input branches code)
 
           (^.` ([(^., [_ {.#Symbol ["" function_name]}]) (^., [_ {.#Symbol ["" arg_name]}])] (^., body)))
           (/function.function analysis function_name arg_name archive body)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/complex.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/complex.lux
index ec4a32d05..42d01ad16 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/complex.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/complex.lux
@@ -113,7 +113,7 @@
         [expectedT (///extension.lifted meta.expected_type)
          expectedT' (/type.check (check.clean (list) expectedT))]
         (/.with_exception ..cannot_analyse_sum [expectedT' lefts right? valueC]
-          (case expectedT
+          (when expectedT
             {.#Sum _}
             (|> (analyse archive valueC)
                 (at ! each (|>> [lefts right?] /.variant))
@@ -129,7 +129,7 @@
             {.#Var id}
             (do !
               [?expectedT' (/type.check (check.peek id))]
-              (case ?expectedT'
+              (when ?expectedT'
                 {.#Some expectedT'}
                 (<| (/type.expecting expectedT')
                     (again valueC))
@@ -152,11 +152,11 @@
                 (again valueC))
             
             {.#Apply inputT funT}
-            (case funT
+            (when funT
               {.#Var funT_id}
               (do !
                 [?funT' (/type.check (check.peek funT_id))]
-                (case ?funT'
+                (when ?funT'
                   {.#Some funT'}
                   (<| (/type.expecting {.#Apply inputT funT'})
                       (again valueC))
@@ -165,7 +165,7 @@
                   (/.except ..invalid_variant_type [expectedT lefts right? valueC])))
 
               _
-              (case (type.applied (list inputT) funT)
+              (when (type.applied (list inputT) funT)
                 {.#Some outputT}
                 (<| (/type.expecting outputT)
                     (again valueC))
@@ -184,7 +184,7 @@
      .let [case_size (list.size group)
            [lefts right?] (/complex.choice case_size idx)]
      expectedT (///extension.lifted meta.expected_type)]
-    (case expectedT
+    (when expectedT
       {.#Var _}
       (do !
         [inferenceT (/inference.variant lefts right? variantT)
@@ -202,7 +202,7 @@
       (is (Operation (List Analysis)))
       (loop (again [membersT+ (type.flat_tuple expectedT)
                     membersC+ members])
-        (case [membersT+ membersC+]
+        (when [membersT+ membersC+]
           [{.#Item memberT {.#End}} {.#Item memberC {.#End}}]
           (<| (at ! each (|>> list))
               (/type.expecting memberT)
@@ -231,7 +231,7 @@
   (do [! ///.monad]
     [expectedT (///extension.lifted meta.expected_type)]
     (/.with_exception ..cannot_analyse_tuple [expectedT membersC]
-      (case expectedT
+      (when expectedT
         {.#Product _}
         (..typed_product analyse expectedT archive membersC)
 
@@ -242,7 +242,7 @@
         {.#Var id}
         (do !
           [?expectedT' (/type.check (check.peek id))]
-          (case ?expectedT'
+          (when ?expectedT'
             {.#Some expectedT'}
             (<| (/type.expecting expectedT')
                 (product analyse archive membersC))
@@ -268,11 +268,11 @@
             (product analyse archive membersC))
 
         {.#Apply inputT funT}
-        (case funT
+        (when funT
           {.#Var funT_id}
           (do !
             [?funT' (/type.check (check.peek funT_id))]
-            (case ?funT'
+            (when ?funT'
               {.#Some funT'}
               (<| (/type.expecting {.#Apply inputT funT'})
                   (product analyse archive membersC))
@@ -281,7 +281,7 @@
               (/.except ..invalid_tuple_type [expectedT membersC])))
 
           _
-          (case (type.applied (list inputT) funT)
+          (when (type.applied (list inputT) funT)
             {.#Some outputT}
             (<| (/type.expecting outputT)
                 (product analyse archive membersC))
@@ -302,7 +302,7 @@
   (loop (again [input record
                 output (is (List [Symbol Code])
                            {.#End})])
-    (case input
+    (when input
       (list.partial [_ {.#Symbol ["" slotH]}] valueH tail)
       (if pattern_matching?
         (///#in {.#None})
@@ -337,7 +337,7 @@
              (do meta.monad
                [head_k (meta.normal head_k)]
                (meta.try (meta.slot head_k))))]
-    (case slotH'
+    (when slotH'
       {try.#Success [_ slot_set recordT]}
       (do !
         [.let [size_record (list.size record)
@@ -351,7 +351,7 @@
                              (function (_ [key val] idx->val)
                                (do !
                                  [key (///extension.lifted (meta.normal key))]
-                                 (case (dictionary.value key tag->idx)
+                                 (when (dictionary.value key tag->idx)
                                    {.#Some idx}
                                    (if (dictionary.key? idx->val idx)
                                      (/.except ..cannot_repeat_slot [key record])
@@ -372,13 +372,13 @@
 
 (def .public (order pattern_matching? record)
   (-> Bit (List [Symbol Code]) (Operation (Maybe [Nat (List Code) Type])))
-  (case record
+  (when record
     ... empty_record = empty_tuple = unit/any = []
     {.#End}
     (///#in {.#Some [0 (list) .Any]})
 
     {.#Item [head_k head_v] _}
-    (case head_k
+    (when head_k
       ["" head_k']
       (if pattern_matching?
         (///#in {.#None})
@@ -394,7 +394,7 @@
 
 (def .public (record analyse archive members)
   (-> Phase Archive (List Code) (Operation Analysis))
-  (case members
+  (when members
     (list)
     //simple.unit
 
@@ -405,9 +405,9 @@
     (do [! ///.monad]
       [head_k (///extension.lifted (meta.normal pseudo_slot))
        slot (///extension.lifted (meta.try (meta.slot head_k)))]
-      (case slot
+      (when slot
         {try.#Success [_ slot_set recordT]}
-        (case (list.size slot_set)
+        (when (list.size slot_set)
           1 (analyse archive singletonC)
           _ (..product analyse archive members))
 
@@ -417,21 +417,21 @@
     _
     (do [! ///.monad]
       [?members (..normal false members)]
-      (case ?members
+      (when ?members
         {.#None}
         (..product analyse archive members)
 
         {.#Some slots}
         (do !
           [record_size,membersC,recordT (..order false slots)]
-          (case record_size,membersC,recordT
+          (when record_size,membersC,recordT
             {.#None}
             (..product analyse archive members)
 
             {.#Some [record_size membersC recordT]}
             (do !
               [expectedT (///extension.lifted meta.expected_type)]
-              (case expectedT
+              (when expectedT
                 {.#Var _}
                 (do !
                   [inferenceT (/inference.record record_size recordT)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/function.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/function.lux
index b14ae34cc..7864fd3d5 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/function.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/function.lux
@@ -59,7 +59,7 @@
     [expectedT (///extension.lifted meta.expected_type)]
     (loop (again [expectedT expectedT])
       (/.with_exception ..cannot_analyse [expectedT function_name arg_name body]
-        (case expectedT
+        (when expectedT
           {.#Function :input: :output:}
           (<| (at ! each (.function (_ [scope bodyA])
                            {/.#Function (list#each (|>> /.variable)
@@ -77,7 +77,7 @@
           (again :anonymous:)
 
           {.#Apply argT funT}
-          (case (type.applied (list argT) funT)
+          (when (type.applied (list argT) funT)
             {.#Some value}
             (again value)
 
@@ -97,7 +97,7 @@
           {.#Var id}
           (do !
             [?expectedT' (/type.check (check.peek id))]
-            (case ?expectedT'
+            (when ?expectedT'
               {.#Some expectedT'}
               (again expectedT')
 
@@ -115,7 +115,7 @@
                      ?:input: (check.try (check.identity (list @output) @input))
                      ? (check.linked? @input @output)
                      _ (<| (check.check expectedT)
-                           (case ?:input:
+                           (when ?:input:
                              {try.#Success :input:}
                              {.#Function :input: (if ?
                                                    :input:
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/reference.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/reference.lux
index cbee3c622..d71fa4ad0 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/reference.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/reference.lux
@@ -45,7 +45,7 @@
   (with_expansions [<return> (in (|> def_name ///reference.constant {/.#Reference}))]
     (do [! ///.monad]
       [constant (///extension.lifted (meta.definition def_name))]
-      (case constant
+      (when constant
         {.#Alias real_def_name}
         (definition quoted_module real_def_name)
         
@@ -91,7 +91,7 @@
   (-> Text (Operation (Maybe Analysis)))
   (do [! ///.monad]
     [?var (/scope.variable var_name)]
-    (case ?var
+    (when ?var
       {.#Some [actualT ref]}
       (do !
         [_ (/type.inference actualT)]
@@ -102,11 +102,11 @@
 
 (def .public (reference quoted_module it)
   (-> Text Symbol (Operation Analysis))
-  (case it
+  (when it
     ["" simple_name]
     (do [! ///.monad]
       [?var (variable simple_name)]
-      (case ?var
+      (when ?var
         {.#Some varA}
         (in varA)
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/case.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/when.lux
index 6c637184c..ceb60e374 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/case.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/analysis/when.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except Pattern case)
+  [lux (.except Pattern when)
    [abstract
     ["[0]" monad (.only do)]]
    [control
@@ -73,7 +73,7 @@
 
 (def (quantified envs baseT)
   (-> (List (List Type)) Type Type)
-  (.case envs
+  (.when envs
     {.#End}
     baseT
 
@@ -81,22 +81,22 @@
     (quantified tail {.#UnivQ head baseT})))
 
 ... Type-checking on the input value is done during the analysis of a
-... "case" expression, to ensure that the patterns being used make
+... "when" expression, to ensure that the patterns being used make
 ... sense for the type of the input value.
 ... Sometimes, that input value is complex, by depending on
 ... type-variables or quantifications.
-... This function makes it easier for "case" analysis to properly
+... This function makes it easier for "when" analysis to properly
 ... type-check the input with respect to the patterns.
 (def .public (tuple :it:)
   (-> Type (Check [(List check.Var) Type]))
   (loop (again [envs (is (List (List Type))
                          (list))
                 :it: :it:])
-    (.case :it:
+    (.when :it:
       {.#Var id}
       (do check.monad
         [?:it:' (check.peek id)]
-        (.case ?:it:'
+        (.when ?:it:'
           {.#Some :it:'}
           (again envs :it:')
 
@@ -118,11 +118,11 @@
       {.#Apply _}
       (do [! check.monad]
         [.let [[:abstraction: :parameters:] (type.flat_application :it:)]
-         :abstraction: (.case :abstraction:
+         :abstraction: (.when :abstraction:
                          {.#Var @abstraction}
                          (do !
                            [?:abstraction: (check.peek @abstraction)]
-                           (.case ?:abstraction:
+                           (.when ?:abstraction:
                              {.#Some :abstraction:}
                              (in :abstraction:)
 
@@ -131,7 +131,7 @@
 
                          _
                          (in :abstraction:))]
-        (.case (type.applied :parameters: :abstraction:)
+        (.when (type.applied :parameters: :abstraction:)
           {.#Some :it:}
           (again envs :it:)
 
@@ -163,13 +163,13 @@
         Type (List Code) (Operation a) (Operation [Pattern a])))
   (do [! ///.monad]
     [[@ex_var+ :input:'] (/type.check (..tuple :input:))]
-    (.case :input:'
+    (.when :input:'
       {.#Product _}
       (let [matches (loop (again [types (type.flat_tuple :input:')
                                   patterns sub_patterns
                                   output (is (List [Type Code])
                                              {.#End})])
-                      (.case [types patterns]
+                      (.when [types patterns]
                         [{.#End} {.#End}]
                         output
 
@@ -226,7 +226,7 @@
 ... pattern, and not separately.
 (def (pattern_analysis num_tags :input: pattern next)
   (All (_ a) (-> (Maybe Nat) Type Code (Operation a) (Operation [Pattern a])))
-  (.case pattern
+  (.when pattern
     [location {.#Symbol ["" name]}]
     (/.with_location location
       (do ///.monad
@@ -254,16 +254,16 @@
       (do [! ///.monad]
         [record (//complex.normal true sub_patterns)
          record_size,members,recordT (is (Operation (Maybe [Nat (List Code) Type]))
-                                         (.case record
+                                         (.when record
                                            {.#Some record}
                                            (//complex.order true record)
 
                                            {.#None}
                                            (in {.#None})))]
-        (.case record_size,members,recordT
+        (.when record_size,members,recordT
           {.#Some [record_size members recordT]}
           (do !
-            [_ (.case :input:
+            [_ (.when :input:
                  {.#Var @input}
                  (/type.check (do check.monad
                                 [? (check.bound? @input)]
@@ -273,7 +273,7 @@
 
                  _
                  (in []))]
-            (.case members
+            (.when members
               (list singleton)
               (pattern_analysis {.#None} :input: singleton next)
 
@@ -287,13 +287,13 @@
     (/.with_location location
       (do ///.monad
         [[@ex_var+ :input:'] (/type.check (..tuple :input:))]
-        (.case :input:'
+        (.when :input:'
           {.#Sum _}
           (let [flat_sum (type.flat_variant :input:')
                 size_sum (list.size flat_sum)
                 num_cases (maybe.else size_sum num_tags)
                 idx (/complex.tag right? lefts)]
-            (.case (list.item idx flat_sum)
+            (.when (list.item idx flat_sum)
               (^.multi {.#Some caseT}
                        (n.< num_cases idx))
               (do ///.monad
@@ -337,9 +337,9 @@
     (/.except ..invalid [pattern])
     ))
 
-(def .public (case analyse branches archive inputC)
+(def .public (when analyse branches archive inputC)
   (-> Phase (List [Code Code]) Phase)
-  (.case branches
+  (.when branches
     {.#Item [patternH bodyH] branchesT}
     (do [! ///.monad]
       [[:input: inputA] (<| /type.inferring
@@ -351,14 +351,14 @@
                            branchesT)
        outputHC (|> outputH product.left /coverage.coverage /.of_try)
        outputTC (monad.each ! (|>> product.left /coverage.coverage /.of_try) outputT)
-       _ (.case (monad.mix try.monad /coverage.composite outputHC outputTC)
+       _ (.when (monad.mix try.monad /coverage.composite outputHC outputTC)
            {try.#Success coverage}
            (///.assertion ..non_exhaustive [inputC branches coverage]
                           (/coverage.exhaustive? coverage))
 
            {try.#Failure error}
            (/.failure error))]
-      (in {/.#Case inputA [outputH outputT]}))
+      (in {/.#When inputA [outputH outputT]}))
 
     {.#End}
     (/.except ..empty_branches [])))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/declaration.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/declaration.lux
index 4fd6f0ed3..cd102ce48 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/declaration.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/declaration.lux
@@ -47,7 +47,7 @@
   (-> Archive ///analysis.Bundle evaluation.Eval
       Eval)
   (function (_ type code lux)
-    (case (compiler_eval archive type code [bundle lux])
+    (when (compiler_eval archive type code [bundle lux])
       {try.#Success [[_bundle lux'] value]}
       {try.#Success [lux' value]}
       
@@ -62,12 +62,12 @@
     (loop (again [state state
                   input expansion
                   output /.no_requirements])
-      (case input
+      (when input
         {.#End}
         {try.#Success [state output]}
         
         {.#Item head tail}
-        (case (phase archive head state)
+        (when (phase archive head state)
           {try.#Success [state' head']}
           (again state' tail (/.merge_requirements head' output))
           
@@ -89,7 +89,7 @@
                                                                 (the [//extension.#state /.#generation /.#phase] state)))
                  extension_eval (as Eval (wrapper (as_expected compiler_eval)))]
            _ (//.with (has [//extension.#state /.#analysis /.#state //extension.#state .#eval] extension_eval state))]
-          (case code
+          (when code
             [_ {.#Form (list.partial [_ {.#Text name}] inputs)}]
             (//extension.apply archive again [name inputs])
 
@@ -99,11 +99,11 @@
                           (do !
                             [macroA (<| (///analysis/type.expecting Macro)
                                         (analysis archive macro))]
-                            (case macroA
+                            (when macroA
                               (///analysis.constant macro_name)
                               (do !
                                 [?macro (//extension.lifted (meta.macro macro_name))
-                                 macro (case ?macro
+                                 macro (when ?macro
                                          {.#Some macro}
                                          (in macro)
                                          
@@ -113,7 +113,7 @@
                               
                               _
                               (//.except ..invalid_macro_call code))))]
-              (case expansion
+              (when expansion
                 (list.partial <lux_def_module> referrals)
                 (|> (again archive <lux_def_module>)
                     (at ! each (revised /.#referrals (list#composite referrals))))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension.lux
index 5606f0a5e..0ad49b88e 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension.lux
@@ -99,7 +99,7 @@
   (All (_ s i o)
     (-> (Extender s i o) Name (Handler s i o) (Operation s i o Any)))
   (function (_ [bundle state])
-    (case (dictionary.has' name (extender handler) bundle)
+    (when (dictionary.has' name (extender handler) bundle)
       {try.#Success bundle'}
       {try.#Success [[bundle' state]
                      []]}
@@ -121,7 +121,7 @@
   (All (_ s i o)
     (-> Archive (Phase s i o) (Extension i) (Operation s i o o)))
   (function (_ (^.let stateE [bundle state]))
-    (case (dictionary.value name bundle)
+    (when (dictionary.value name bundle)
       {.#Some handler}
       (((handler name phase) archive parameters)
        stateE)
@@ -136,7 +136,7 @@
   (function (_ operation)
     (function (_ [bundle state])
       (let [old (get state)]
-        (case (operation [bundle (set (transform old) state)])
+        (when (operation [bundle (set (transform old) state)])
           {try.#Success [[bundle' state'] output]}
           {try.#Success [[bundle' (set old state')] output]}
 
@@ -149,7 +149,7 @@
         (-> (Operation s i o v) (Operation s i o v))))
   (function (_ operation)
     (function (_ [bundle state])
-      (case (operation [bundle (transform state)])
+      (when (operation [bundle (transform state)])
         {try.#Success [[bundle' state'] output]}
         {try.#Success [[bundle' state] output]}
 
@@ -177,7 +177,7 @@
   (All (_ s i o v)
     (-> (//.Operation s v) (Operation s i o v)))
   (function (_ [bundle state])
-    (case (action state)
+    (when (action state)
       {try.#Success [state' output]}
       {try.#Success [[bundle state'] output]}
 
@@ -188,7 +188,7 @@
   (All (_ s i o v)
     (-> (Operation s i o v) (//.Operation s v)))
   (function (_ state)
-    (case (it [..empty state])
+    (when (it [..empty state])
       {try.#Success [[_ state'] output]}
       {try.#Success [state' output]}
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/analysis/jvm.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/analysis/jvm.lux
index e072e7d9d..9b8eabe1b 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/analysis/jvm.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/analysis/jvm.lux
@@ -395,16 +395,16 @@
 
 (def lux_array_type
   (template (_ :read: :write:)
-    [{.#Primitive array.type_name (list {.#Apply :write: {.#Apply :read: _Mutable}})}]))
+    [{.#Primitive array.primitive (list {.#Apply :write: {.#Apply :read: _Mutable}})}]))
 
 (def (jvm_type luxT)
   (-> .Type (Operation (Type Value)))
-  (case luxT
+  (when luxT
     {.#Named name anonymousT}
     (jvm_type anonymousT)
     
     {.#Apply inputT abstractionT}
-    (case (type.applied (list inputT) abstractionT)
+    (when (type.applied (list inputT) abstractionT)
       {.#Some outputT}
       (jvm_type outputT)
 
@@ -415,9 +415,9 @@
     (phase#each jvm.array (jvm_type elemT))
 
     {.#Primitive class parametersT}
-    (case (dictionary.value class ..boxes)
+    (when (dictionary.value class ..boxes)
       {.#Some [_ primitive_type]}
-      (case parametersT
+      (when parametersT
         {.#End}
         (phase#in primitive_type)
 
@@ -431,7 +431,7 @@
                                       (function (_ parameterT)
                                         (do phase.monad
                                           [parameterJT (jvm_type parameterT)]
-                                          (case (parser.parameter? parameterJT)
+                                          (when (parser.parameter? parameterJT)
                                             {.#Some parameterJT}
                                             (in parameterJT)
                                             
@@ -461,7 +461,7 @@
 (def (primitive_array_length_handler primitive_type)
   (-> (Type Primitive) Handler)
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list arrayC)
       (do phase.monad
         [_ (typeA.inference ..int)
@@ -477,7 +477,7 @@
 (def array::length::object
   Handler
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list arrayC)
       (<| typeA.with_var
           (function (_ [@read :read:]))
@@ -499,7 +499,7 @@
 (def (new_primitive_array_handler primitive_type)
   (-> (Type Primitive) Handler)
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list lengthC)
       (do phase.monad
         [lengthA (<| (typeA.expecting ..int)
@@ -514,14 +514,14 @@
 (def array::new::object
   Handler
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list lengthC)
       (do phase.monad
         [lengthA (<| (typeA.expecting ..int)
                      (analyse archive lengthC))
          expectedT (///.lifted meta.expected_type)
          expectedJT (jvm_array_type expectedT)
-         elementJT (case (parser.array? expectedJT)
+         elementJT (when (parser.array? expectedJT)
                      {.#Some elementJT}
                      (in elementJT)
                      
@@ -535,7 +535,7 @@
 
 (def (check_parameter objectT)
   (-> .Type (Operation (Type Parameter)))
-  (case objectT
+  (when objectT
     (lux_array_type elementT _)
     (/////analysis.except ..non_parameter objectT)
     
@@ -563,7 +563,7 @@
     {.#Var @var}
     (do phase.monad
       [:var: (typeA.check (check.peek @var))]
-      (case :var:
+      (when :var:
         {.#Some :var:}
         (check_parameter :var:)
         
@@ -581,7 +581,7 @@
      [.#ExQ])
 
     {.#Apply inputT abstractionT}
-    (case (type.applied (list inputT) abstractionT)
+    (when (type.applied (list inputT) abstractionT)
       {.#Some outputT}
       (check_parameter outputT)
 
@@ -596,7 +596,7 @@
 
 (def (check_jvm objectT)
   (-> .Type (Operation (Type Value)))
-  (case objectT
+  (when objectT
     {.#Primitive name {.#End}}
     (`` (cond (,, (with_template [<type>]
                     [(text#= (..reflection <type>) name)
@@ -652,7 +652,7 @@
      [.#ExQ])
 
     {.#Apply inputT abstractionT}
-    (case (type.applied (list inputT) abstractionT)
+    (when (type.applied (list inputT) abstractionT)
       {.#Some outputT}
       (check_jvm outputT)
 
@@ -665,7 +665,7 @@
 (with_template [<name> <category> <parser>]
   [(def .public (<name> mapping typeJ)
      (-> Mapping (Type <category>) (Operation .Type))
-     (case (|> typeJ ..signature (<text>.result (<parser> mapping)))
+     (when (|> typeJ ..signature (<text>.result (<parser> mapping)))
        {try.#Success check}
        (typeA.check check)
        
@@ -698,7 +698,7 @@
 (def (read_primitive_array_handler lux_type jvm_type)
   (-> .Type (Type Primitive) Handler)
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list idxC arrayC)
       (do phase.monad
         [_ (typeA.inference lux_type)
@@ -715,7 +715,7 @@
 (def array::read::object
   Handler
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list idxC arrayC)
       (<| typeA.with_var
           (function (_ [@read :read:]))
@@ -742,7 +742,7 @@
   (let [array_type {.#Primitive (|> (jvm.array jvm_type) ..reflection)
                                 (list)}]
     (function (_ extension_name analyse archive args)
-      (case args
+      (when args
         (list idxC valueC arrayC)
         (do phase.monad
           [_ (typeA.inference array_type)
@@ -762,7 +762,7 @@
 (def array::write::object
   Handler
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list idxC valueC arrayC)
       (<| typeA.with_var
           (function (_ [@read :read:]))
@@ -840,7 +840,7 @@
 (def object::null
   Handler
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list)
       (do phase.monad
         [expectedT (///.lifted meta.expected_type)
@@ -854,7 +854,7 @@
 (def object::null?
   Handler
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list objectC)
       (do phase.monad
         [_ (typeA.inference .Bit)
@@ -869,7 +869,7 @@
 (def object::synchronized
   Handler
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list monitorC exprC)
       (do phase.monad
         [[monitorT monitorA] (typeA.inferring
@@ -884,7 +884,7 @@
 (def (object::throw class_loader)
   (-> java/lang/ClassLoader Handler)
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list exceptionC)
       (do phase.monad
         [_ (typeA.inference Nothing)
@@ -904,9 +904,9 @@
 (def (object::class class_loader)
   (-> java/lang/ClassLoader Handler)
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list classC)
-      (case classC
+      (when classC
         [_ {.#Text class}]
         (do phase.monad
           [_ (..ensure_fresh_class! class_loader class)
@@ -949,7 +949,7 @@
                      super_class (phase.lifted (reflection!.load class_loader super_name))
                      superT (reflection_type mapping superJT)]
                     (in [[super_name superT] (java/lang/Class::isAssignableFrom super_class to_class)])))
-                (case (java/lang/Class::getGenericSuperclass from_class)
+                (when (java/lang/Class::getGenericSuperclass from_class)
                   {.#Some super}
                   (list.partial super (array.list {.#None} (java/lang/Class::getGenericInterfaces from_class)))
 
@@ -962,7 +962,7 @@
 (def (object::cast class_loader)
   (-> java/lang/ClassLoader Handler)
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list fromC)
       (do [! phase.monad]
         [toT (///.lifted meta.expected_type)
@@ -1006,7 +1006,7 @@
                                          (do !
                                            [candidate_parents (is (Operation (List [[Text .Type] Bit]))
                                                                   (class_candidate_parents class_loader current_name currentT to_name to_class))]
-                                           (case (|> candidate_parents
+                                           (when (|> candidate_parents
                                                      (list.only product.right)
                                                      (list#each product.left))
                                              {.#Item [next_name nextT] _}
@@ -1014,7 +1014,7 @@
 
                                              {.#End}
                                              (in false)))))
-                                     (in (case [(type#= java/lang/Object fromT)
+                                     (in (when [(type#= java/lang/Object fromT)
                                                 (parser.array? toJT)]
                                            [.true {.#Some _}]
                                            true
@@ -1154,21 +1154,21 @@
 (def (de_aliased aliasing)
   (-> Aliasing (Type Value) (Type Value))
   (function (again it)
-    (`` (<| (case (parser.var? it)
+    (`` (<| (when (parser.var? it)
               {.#Some name}
               (|> aliasing
                   (dictionary.value name)
                   (maybe#each jvm.var)
                   (maybe.else it))
               {.#None})
-            (case (parser.class? it)
+            (when (parser.class? it)
               {.#Some [name parameters]}
               (|> parameters
                   (list#each (|>> again (as (Type Parameter))))
                   (jvm.class name))
               {.#None})
             (,, (with_template [<read> <as> <write>]
-                  [(case (<read> it)
+                  [(when (<read> it)
                      {.#Some :sub:}
                      (<write> (as (Type <as>) (again :sub:)))
                      {.#None})]
@@ -1189,13 +1189,13 @@
      .let [modifiers (java/lang/reflect/Method::getModifiers method)
            correct_class? (java/lang/Class::isAssignableFrom class (java/lang/reflect/Method::getDeclaringClass method))
            correct_method? (text#= method_name (java/lang/reflect/Method::getName method))
-           same_static? (case method_style
+           same_static? (when method_style
                           {#Static}
                           (java/lang/reflect/Modifier::isStatic modifiers)
 
                           _
                           true)
-           same_special? (case method_style
+           same_special? (when method_style
                            {#Special}
                            (not (or (java/lang/reflect/Modifier::isInterface (java/lang/Class::getModifiers class))
                                     (java/lang/reflect/Modifier::isAbstract modifiers)))
@@ -1262,7 +1262,7 @@
 (def (return_type it)
   (-> java/lang/reflect/Method (Try (Type Return)))
   (reflection!.return
-   (case (java/lang/reflect/Method::getGenericReturnType it)
+   (when (java/lang/reflect/Method::getGenericReturnType it)
      {.#Some it}
      it
      
@@ -1272,7 +1272,7 @@
 (def (method_signature method_style method)
   (-> Method_Style java/lang/reflect/Method (Operation Method_Signature))
   (let [owner (java/lang/reflect/Method::getDeclaringClass method)
-        owner_tvars (case method_style
+        owner_tvars (when method_style
                       {#Static}
                       (list)
 
@@ -1303,7 +1303,7 @@
                               (phase#each (monad.each ! (..reflection_type mapping)))
                               phase#conjoint)
        .let [methodT (<| (type.univ_q (dictionary.size mapping))
-                         (type.function (case method_style
+                         (type.function (when method_style
                                           {#Static}
                                           inputsT
 
@@ -1358,7 +1358,7 @@
 (with_template [<name> <tag>]
   [(def <name>
      (-> Evaluation (Maybe Method_Signature))
-     (|>> (pipe.case
+     (|>> (pipe.when
             {<tag> output}
             {.#Some output}
 
@@ -1391,7 +1391,7 @@
   (-> (java/lang/Class java/lang/Object)
       (List (java/lang/Class java/lang/Object)))
   (let [interfaces (array.list {.#None} (java/lang/Class::getInterfaces it))
-        supers (case (java/lang/Class::getSuperclass it)
+        supers (when (java/lang/Class::getSuperclass it)
                  {.#Some class}
                  (list.partial class interfaces)
                  
@@ -1440,7 +1440,7 @@
                                                        (|>> {#Pass})
                                                        (|>> {#Hint}))
                                               (method_signature method_style method)))))))]
-    (case (list.all pass candidates)
+    (when (list.all pass candidates)
       {.#Item method {.#End}}
       (in method)
 
@@ -1474,7 +1474,7 @@
                                             (|>> {#Pass})
                                             (|>> {#Hint}))
                                           (constructor_signature constructor))))))]
-    (case (list.all pass candidates)
+    (when (list.all pass candidates)
       {.#Item constructor {.#End}}
       (in constructor)
 
@@ -1539,7 +1539,7 @@
          _ (phase.assertion ..deprecated_method [class method methodT]
                             (not deprecated?))
          [outputT allA] (inference.general archive analyse methodT (list.partial objectC (list#each product.right argsTC)))
-         .let [[objectA argsA] (case allA
+         .let [[objectA argsA] (when allA
                                  {.#Item objectA argsA}
                                  [objectA argsA]
 
@@ -1564,7 +1564,7 @@
          _ (phase.assertion ..deprecated_method [class method methodT]
                             (not deprecated?))
          [outputT allA] (inference.general archive analyse methodT (list.partial objectC (list#each product.right argsTC)))
-         .let [[objectA argsA] (case allA
+         .let [[objectA argsA] (when allA
                                  {.#Item objectA argsA}
                                  [objectA argsA]
 
@@ -1592,7 +1592,7 @@
          _ (phase.assertion ..deprecated_method [class_name method methodT]
                             (not deprecated?))
          [outputT allA] (inference.general archive analyse methodT (list.partial objectC (list#each product.right argsTC)))
-         .let [[objectA argsA] (case allA
+         .let [[objectA argsA] (when allA
                                  {.#Item objectA argsA}
                                  [objectA argsA]
 
@@ -1790,7 +1790,7 @@
 
 (def .public (visibility_analysis visibility)
   (-> Visibility Analysis)
-  (/////analysis.text (case visibility
+  (/////analysis.text (when visibility
                         {#Public} ..public_tag
                         {#Private} ..private_tag
                         {#Protected} ..protected_tag
@@ -1897,13 +1897,13 @@
 
 (def (with_fake_parameter#pattern it)
   (-> pattern.Pattern pattern.Pattern)
-  (case it
+  (when it
     {pattern.#Simple _}
     it
     
     {pattern.#Complex it}
     {pattern.#Complex
-     (case it
+     (when it
        {complex.#Variant it}
        {complex.#Variant (revised complex.#value with_fake_parameter#pattern it)}
 
@@ -1915,13 +1915,13 @@
 
 (def (with_fake_parameter it)
   (-> Analysis Analysis)
-  (case it
+  (when it
     {/////analysis.#Simple _}
     it
 
     {/////analysis.#Structure it}
     {/////analysis.#Structure
-     (case it
+     (when it
        {complex.#Variant it}
        {complex.#Variant (revised complex.#value with_fake_parameter it)}
 
@@ -1930,10 +1930,10 @@
 
     {/////analysis.#Reference it}
     {/////analysis.#Reference
-     (case it
+     (when it
        {reference.#Variable it}
        {reference.#Variable
-        (case it
+        (when it
           {variable.#Local it}
           {variable.#Local (++ it)}
           
@@ -1943,8 +1943,8 @@
        {reference.#Constant _}
        it)}
     
-    {/////analysis.#Case value [head tail]}
-    {/////analysis.#Case (with_fake_parameter value)
+    {/////analysis.#When value [head tail]}
+    {/////analysis.#When (with_fake_parameter value)
                          (let [with_fake_parameter (is (-> /////analysis.Branch /////analysis.Branch)
                                                        (|>> (revised /////analysis.#when with_fake_parameter#pattern)
                                                             (revised /////analysis.#then with_fake_parameter)))]
@@ -1967,13 +1967,13 @@
   (-> Nat Analysis Analysis)
   (<| /////analysis.tuple
       (list (/////analysis.unit))
-      (case arity
+      (when arity
         (^.or 0 1)
         bodyA
         
         2
         (let [forced_refencing (/////analysis.tuple (list#each (|>> /////analysis.local) (list.indices (++ arity))))]
-          {/////analysis.#Case (/////analysis.unit)
+          {/////analysis.#When (/////analysis.unit)
                                [[/////analysis.#when
                                  {pattern.#Bind 2}
                                  
@@ -1983,7 +1983,7 @@
 
         _
         (let [forced_refencing (/////analysis.tuple (list#each (|>> /////analysis.local) (list.indices (++ arity))))]
-          {/////analysis.#Case (/////analysis.unit)
+          {/////analysis.#When (/////analysis.unit)
                                [[/////analysis.#when
                                  {pattern.#Complex
                                   {complex.#Tuple
@@ -2044,7 +2044,7 @@
                                       (list#each (|>> /////analysis.variable)
                                                  (scope.environment scope))
                                       (<| (..hidden_method_body arity)
-                                          (case arity
+                                          (when arity
                                             0 (with_fake_parameter bodyA)
                                             _ bodyA))}
                                      ))))))
@@ -2148,7 +2148,7 @@
                                       (list#each (|>> /////analysis.variable)
                                                  (scope.environment scope))
                                       (<| (..hidden_method_body arity)
-                                          (case arity
+                                          (when arity
                                             0 (with_fake_parameter bodyA)
                                             _ bodyA))}
                                      ))))))
@@ -2274,7 +2274,7 @@
 (def (override_mapping mapping supers parent_type)
   (-> Mapping (List (Type Class)) (Type Class) (Operation (List [Text .Type])))
   (let [[parent_name parent_parameters] (parser.read_class parent_type)]
-    (case (list.one (function (_ super)
+    (when (list.one (function (_ super)
                       (let [[super_name super_parameters] (parser.read_class super)]
                         (if (text#= parent_name super_name)
                           {.#Some super_parameters}
@@ -2353,7 +2353,7 @@
                                       (list#each (|>> /////analysis.variable)
                                                  (scope.environment scope))
                                       (<| (..hidden_method_body arity)
-                                          (case arity
+                                          (when arity
                                             0 (with_fake_parameter bodyA)
                                             _ bodyA))}
                                      ))))))
@@ -2397,7 +2397,7 @@
                              (list.size actual_parameters)))]
     (in (|> (list.zipped_2 expected_parameters actual_parameters)
             (list#mix (function (_ [expected actual] mapping)
-                        (case (parser.var? actual)
+                        (when (parser.var? actual)
                           {.#Some actual}
                           (dictionary.has actual expected mapping)
                           
@@ -2493,17 +2493,17 @@
 
 (def (field_definition field)
   (-> Field (Resource field.Field))
-  (case field
+  (when field
     ... TODO: Handle annotations.
     {#Constant [name annotations type value]}
-    (case value
+    (when value
       (^.with_template [<tag> <type> <constant>]
         [[_ {<tag> value}]
          (do pool.monad
            [constant (`` (|> value (,, (template.spliced <constant>))))
             attribute (attribute.constant constant)]
            (field.field ..constant::modifier name true <type> (sequence.sequence attribute)))])
-      ([.#Bit jvm.boolean [(pipe.case #0 +0 #1 +1) .i64 i32.i32 constant.integer pool.integer]]
+      ([.#Bit jvm.boolean [(pipe.when #0 +0 #1 +1) .i64 i32.i32 constant.integer pool.integer]]
        [.#Int jvm.byte [.i64 i32.i32 constant.integer pool.integer]]
        [.#Int jvm.short [.i64 i32.i32 constant.integer pool.integer]]
        [.#Int jvm.int [.i64 i32.i32 constant.integer pool.integer]]
@@ -2525,7 +2525,7 @@
 
 (def method_privacy
   (-> ffi.Privacy (Modifier method.Method))
-  (|>> (pipe.case
+  (|>> (pipe.when
          {ffi.#PublicP} method.public
          {ffi.#PrivateP} method.private
          {ffi.#ProtectedP} method.protected
@@ -2536,7 +2536,7 @@
 
 (def (mock_value valueT)
   (-> (Type Value) (Bytecode Any))
-  (case (jvm.primitive? valueT)
+  (when (jvm.primitive? valueT)
     {.#Left classT}
     _.aconst_null
     
@@ -2555,14 +2555,14 @@
 
 (def (mock_return :return:)
   (-> (Type Return) (Bytecode Any))
-  (case (jvm.void? :return:)
+  (when (jvm.void? :return:)
     {.#Right :return:}
     _.return
 
     {.#Left valueT}
     (all _.composite
          (mock_value valueT)
-         (case (jvm.primitive? valueT)
+         (when (jvm.primitive? valueT)
            {.#Left classT}
            _.areturn
            
@@ -2581,7 +2581,7 @@
 
 (def (mock_method super method)
   (-> (Type Class) (Method_Definition Code) (Resource method.Method))
-  (case method
+  (when method
     {#Constructor [privacy strict_floating_point? annotations variables exceptions
                    self arguments constructor_arguments
                    body]}
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/analysis/lux.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/analysis/lux.lux
index df5a61fc9..98912da07 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/analysis/lux.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/analysis/lux.lux
@@ -42,7 +42,7 @@
          (-> Text Phase Archive s (Operation Analysis))]
         Handler))
   (function (_ extension_name analyse archive args)
-    (case (<code>.result syntax args)
+    (when (<code>.result syntax args)
       {try.#Success inputs}
       (handler extension_name analyse archive inputs)
 
@@ -91,7 +91,7 @@
    (Parser text.Char)
    (do <>.monad
      [raw <code>.text]
-     (case (text.size raw)
+     (when (text.size raw)
        1 (in (|> raw (text.char 0) maybe.trusted))
        _ (<>.failure (exception.error ..char_text_must_be_size_1 [raw])))))
 
@@ -137,7 +137,7 @@
 (def lux::try
   Handler
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list opC)
       (<| typeA.with_var
           (function (_ [@var :var:]))
@@ -154,7 +154,7 @@
 (def lux::in_module
   Handler
   (function (_ extension_name analyse archive argsC+)
-    (case argsC+
+    (when argsC+
       (list [_ {.#Text module_name}] exprC)
       (////analysis.with_current_module module_name
         (analyse archive exprC))
@@ -165,7 +165,7 @@
 (def (lux::type::check eval)
   (-> Eval Handler)
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list typeC valueC)
       (do [! ////.monad]
         [actualT (at ! each (|>> (as Type))
@@ -180,7 +180,7 @@
 (def (lux::type::as eval)
   (-> Eval Handler)
   (function (_ extension_name analyse archive args)
-    (case args
+    (when args
       (list typeC valueC)
       (do [! ////.monad]
         [actualT (at ! each (|>> (as Type))
@@ -217,7 +217,7 @@
          input_type (loop (again [input_name (symbol .Macro')])
                       (do !
                         [input_type (///.lifted (meta.definition (symbol .Macro')))]
-                        (case input_type
+                        (when input_type
                           (^.or {.#Definition [exported? def_type def_value]}
                                 {.#Type [exported? def_value labels]})
                           (in (as Type def_value))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/declaration/jvm.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/declaration/jvm.lux
index 16dc3bc08..942f931d8 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/declaration/jvm.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/declaration/jvm.lux
@@ -103,7 +103,7 @@
 
 (def method_privacy
   (-> ffi.Privacy (Modifier method.Method))
-  (|>> (pipe.case
+  (|>> (pipe.when
          {ffi.#PublicP} method.public
          {ffi.#PrivateP} method.private
          {ffi.#ProtectedP} method.protected
@@ -227,17 +227,17 @@
 
 (def (field_definition field)
   (-> Field (Resource field.Field))
-  (case field
+  (when field
     ... TODO: Handle annotations.
     {#Constant [name annotations type value]}
-    (case value
+    (when value
       (^.with_template [<tag> <type> <constant>]
         [[_ {<tag> value}]
          (do pool.monad
            [constant (`` (|> value (,, (template.spliced <constant>))))
             attribute (attribute.constant constant)]
            (field.field ..constant::modifier name true <type> (sequence.sequence attribute)))])
-      ([.#Bit type.boolean [(pipe.case #0 +0 #1 +1) .i64 i32.i32 constant.integer pool.integer]]
+      ([.#Bit type.boolean [(pipe.when #0 +0 #1 +1) .i64 i32.i32 constant.integer pool.integer]]
        [.#Int type.byte [.i64 i32.i32 constant.integer pool.integer]]
        [.#Int type.short [.i64 i32.i32 constant.integer pool.integer]]
        [.#Int type.int [.i64 i32.i32 constant.integer pool.integer]]
@@ -414,7 +414,7 @@
 
 (def (method_argument lux_register argumentT jvm_register)
   (-> Register (Type Value) Register [Register (Bytecode Any)])
-  (case (type.primitive? argumentT)
+  (when (type.primitive? argumentT)
     {.#Left argumentT}
     [(n.+ 1 jvm_register)
      (if (n.= lux_register jvm_register)
@@ -460,7 +460,7 @@
   (<| (let [[privacy strict_floating_point? annotations method_tvars exceptions
              self arguments constructor_argumentsS
              bodyS] method
-             bodyS (case (list.size arguments)
+             bodyS (when (list.size arguments)
                      0 (host.without_fake_parameter bodyS)
                      _ bodyS)])
       (do [! phase.monad]
@@ -495,14 +495,14 @@
 
 (def (method_return returnT)
   (-> (Type Return) (Bytecode Any))
-  (case (type.void? returnT)
+  (when (type.void? returnT)
     {.#Right returnT}
     _.return
 
     {.#Left returnT}
-    (case (type.primitive? returnT)
+    (when (type.primitive? returnT)
       {.#Left returnT}
-      (case (type.class? returnT)
+      (when (type.class? returnT)
         {.#Some class_name}
         (all _.composite
              (_.checkcast returnT)
@@ -537,7 +537,7 @@
     [.let [[super method_name strict_floating_point? annotations
             method_tvars self arguments returnJ exceptionsJ
             bodyS] method
-            bodyS (case (list.size arguments)
+            bodyS (when (list.size arguments)
                     0 (host.without_fake_parameter bodyS)
                     _ bodyS)]
      generate declaration.generation]
@@ -564,7 +564,7 @@
     [.let [[method_name privacy final? strict_floating_point? annotations method_tvars
             self arguments returnJ exceptionsJ
             bodyS] method
-            bodyS (case (list.size arguments)
+            bodyS (when (list.size arguments)
                     0 (host.without_fake_parameter bodyS)
                     _ bodyS)]
      generate declaration.generation]
@@ -627,7 +627,7 @@
 
 (def (method_generation archive super_class method)
   (-> Archive (Type Class) (Method_Definition Synthesis) (Operation (Resource Method)))
-  (case method
+  (when method
     {#Constructor method}
     (..constructor_method_generation archive super_class method)
     
@@ -656,7 +656,7 @@
     (do phase.monad
       [methodA (is (Operation Analysis)
                    (declaration.lifted_analysis
-                    (case methodC
+                    (when methodC
                       {#Constructor method}
                       (jvm.analyse_constructor_method analyse archive selfT mapping method)
 
@@ -709,7 +709,7 @@
 
 (def (mock_value valueT)
   (-> (Type Value) (Bytecode Any))
-  (case (type.primitive? valueT)
+  (when (type.primitive? valueT)
     {.#Left classT}
     _.aconst_null
     
@@ -728,14 +728,14 @@
 
 (def (mock_return returnT)
   (-> (Type Return) (Bytecode Any))
-  (case (type.void? returnT)
+  (when (type.void? returnT)
     {.#Right returnT}
     _.return
 
     {.#Left valueT}
     (all _.composite
          (mock_value valueT)
-         (case (type.primitive? valueT)
+         (when (type.primitive? valueT)
            {.#Left classT}
            _.areturn
            
@@ -754,7 +754,7 @@
 
 (def (mock_method super method)
   (-> (Type Class) (Method_Definition Code) (Resource method.Method))
-  (case method
+  (when method
     {#Constructor [privacy strict_floating_point? annotations variables exceptions
                    self arguments constructor_arguments
                    body]}
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/declaration/lux.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/declaration/lux.lux
index 4b93daa97..c917dd6a0 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/declaration/lux.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/declaration/lux.lux
@@ -66,7 +66,7 @@
              (Operation anchor expression declaration Requirements))]
         (Handler anchor expression declaration)))
   (function (_ extension_name phase archive inputs)
-    (case (<code>.result syntax inputs)
+    (when (<code>.result syntax inputs)
       {try.#Success inputs}
       (handler extension_name phase archive inputs)
 
@@ -126,7 +126,7 @@
      [dependencies (cache/artifact.dependencies archive codeS)
       [interim_artifacts codeG] (/////generation.with_interim_artifacts archive
                                   (generate archive codeS))
-      .let [@abstraction (case codeS
+      .let [@abstraction (when codeS
                            (/////synthesis.function/abstraction [env arity body])
                            (|> interim_artifacts
                                list.last
@@ -152,7 +152,7 @@
      [_ code//type codeA] (/////declaration.lifted_analysis
                            (scope.with
                              (typeA.fresh
-                              (case expected
+                              (when expected
                                 {.#None}
                                 (do !
                                   [[code//type codeA] (typeA.inferring
@@ -245,7 +245,7 @@
 (def (lux::def expander host_analysis)
   (-> Expander /////analysis.Bundle Handler)
   (function (_ extension_name phase archive inputsC+)
-    (case inputsC+
+    (when inputsC+
       (list [_ {.#Symbol ["" short_name]}] valueC exported?C)
       (do phase.monad
         [current_module (/////declaration.lifted_analysis
@@ -288,13 +288,13 @@
          [type valueT value] (..definition archive full_name {.#Some .Type} valueC)
          labels (/////declaration.lifted_analysis
                  (do phase.monad
-                   [.let [[record? labels] (case labels
+                   [.let [[record? labels] (when labels
                                              {.#Left tags}
                                              [false tags]
                                              
                                              {.#Right slots}
                                              [true slots])]
-                    _ (case labels
+                    _ (when labels
                         {.#End}
                         (moduleA.define short_name {.#Definition [exported? type value]})
 
@@ -325,7 +325,7 @@
             (monad.each ! (function (_ [module alias])
                             (do !
                               [_ (moduleA.import module)]
-                              (case alias
+                              (when alias
                                 "" (in [])
                                 _ (moduleA.alias alias module))))
                         imports))]
@@ -351,7 +351,7 @@
   (do phase.monad
     [current_module (///.lifted meta.current_module_name)
      constant (///.lifted (meta.definition original))]
-    (case constant
+    (when constant
       {.#Alias de_aliased}
       (phase.except ..cannot_alias_an_alias [[current_module alias] original de_aliased])
       
@@ -393,7 +393,7 @@
   (function (again type)
     (if (type#= original type)
       replacement
-      (case type
+      (when type
         {.#Primitive name parameters}
         {.#Primitive name (list#each again parameters)}
 
@@ -425,7 +425,7 @@
        (-> [Type Type Type] Extender
            (Handler anchor expression declaration)))
      (function (handler extension_name phase archive inputsC+)
-       (case inputsC+
+       (when inputsC+
          (list nameC valueC)
          (do phase.monad
            [target_platform (/////declaration.lifted_analysis
@@ -433,7 +433,7 @@
             [_ _ name] (evaluate! archive Text nameC)
             [_ handlerV] (<definer> archive (as Text name)
                                     (let [raw_type (type_literal <def_type>)]
-                                      (case target_platform
+                                      (when target_platform
                                         (^.or @.jvm
                                               @.js)
                                         raw_type
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/common_lisp/common.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/common_lisp/common.lux
index 41b1165c9..cda183698 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/common_lisp/common.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/common_lisp/common.lux
@@ -31,7 +31,7 @@
     ["[0]" reference]
     ["//" common_lisp
      ["[1][0]" runtime (.only Operation Phase Handler Bundle Generator)]
-     ["[1][0]" case]]]
+     ["[1][0]" when]]]
    [//
     ["[0]" generation]
     ["[0]" synthesis (.only %synthesis)
@@ -45,7 +45,7 @@
          (-> Text (Generator s))]
         Handler))
   (function (_ extension_name phase archive input)
-    (case (<s>.result parser input)
+    (when (<s>.result parser input)
       {try.#Success input'}
       (handler extension_name phase archive input')
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/js/common.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/js/common.lux
index 772660310..d6db61d49 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/js/common.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/js/common.lux
@@ -31,7 +31,7 @@
      ["[1][0]" primitive]
      ["[1][0]" structure]
      ["[1][0]" reference]
-     ["[1][0]" case]
+     ["[1][0]" when]
      ["[1][0]" loop]
      ["[1][0]" function]]]
    [//
@@ -46,7 +46,7 @@
          (-> Text (Generator s))]
         Handler))
   (function (_ extension_name phase archive input)
-    (case (<s>.result parser input)
+    (when (<s>.result parser input)
       {try.#Success input'}
       (handler extension_name phase archive input')
 
@@ -101,7 +101,7 @@
 
 (def .public (statement expression archive synthesis)
   Phase!
-  (case synthesis
+  (when synthesis
     ... TODO: Get rid of this ASAP
     {synthesis.#Extension "lux syntax char case!" parameters}
     (do /////.monad
@@ -126,17 +126,17 @@
     ([synthesis.#Reference]
      [synthesis.#Extension])
 
-    (synthesis.branch/case case)
-    (//case.case! statement expression archive case)
+    (synthesis.branch/when when)
+    (//when.when! statement expression archive when)
 
     (synthesis.branch/exec it)
-    (//case.exec! statement expression archive it)
+    (//when.exec! statement expression archive it)
 
     (synthesis.branch/let let)
-    (//case.let! statement expression archive let)
+    (//when.let! statement expression archive let)
 
     (synthesis.branch/if if)
-    (//case.if! statement expression archive if)
+    (//when.if! statement expression archive if)
 
     (synthesis.loop/scope scope)
     (//loop.scope! statement expression archive scope)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/js/host.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/js/host.lux
index b15b0ae3f..2f7766332 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/js/host.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/js/host.lux
@@ -143,7 +143,7 @@
         (in (_.closure g!inputs
                        (all _.then
                             (_.define g!abstraction abstractionG)
-                            (_.return (case (.nat arity)
+                            (_.return (when (.nat arity)
                                         0 (_.apply_1 g!abstraction //runtime.unit)
                                         1 (_.apply g!abstraction g!inputs)
                                         _ (_.apply_1 g!abstraction (_.array g!inputs)))))))))]))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/jvm/common.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/jvm/common.lux
index 9520433e1..bc81d188e 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/jvm/common.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/jvm/common.lux
@@ -49,7 +49,7 @@
          (-> Text Phase Archive s (Operation (Bytecode Any)))]
         Handler))
   (function (_ extension_name phase archive input)
-    (case (<synthesis>.result parser input)
+    (when (<synthesis>.result parser input)
       {try.#Success input'}
       (handler extension_name phase archive input')
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/jvm/host.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/jvm/host.lux
index ced11c93e..0d7953920 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/jvm/host.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/jvm/host.lux
@@ -372,9 +372,9 @@
   (Parser (Type Object))
   (do <>.monad
     [arrayJT (<text>.then parser.array <synthesis>.text)]
-    (case (parser.array? arrayJT)
+    (when (parser.array? arrayJT)
       {.#Some elementJT}
-      (case (parser.object? elementJT)
+      (when (parser.object? elementJT)
         {.#Some elementJT}
         (in elementJT)
 
@@ -665,7 +665,7 @@
         [valueG (generate archive valueS)]
         (in (all _.composite
                  valueG
-                 (case (parser.object? :unboxed:)
+                 (when (parser.object? :unboxed:)
                    {.#Some :unboxed:}
                    (_.checkcast :unboxed:)
                    
@@ -697,7 +697,7 @@
         [valueG (generate archive valueS)
          objectG (generate archive objectS)
          .let [:class: (type.class class (list))
-               putG (case (parser.object? :unboxed:)
+               putG (when (parser.object? :unboxed:)
                       {.#Some :unboxed:}
                       (all _.composite
                            (_.checkcast :unboxed:)
@@ -723,7 +723,7 @@
   (-> Phase Archive Input (Operation (Typed (Bytecode Any))))
   (do //////.monad
     [valueG (generate archive valueS)]
-    (case (type.primitive? valueT)
+    (when (type.primitive? valueT)
       {.#Right valueT}
       (in [valueT valueG])
       
@@ -734,7 +734,7 @@
 
 (def (prepare_output outputT)
   (-> (Type Return) (Bytecode Any))
-  (case (type.void? outputT)
+  (when (type.void? outputT)
     {.#Right outputT}
     ..unitG
     
@@ -825,7 +825,7 @@
 (def .public (hidden_method_body arity body)
   (-> Nat Synthesis Synthesis)
   (with_expansions [<oops> (panic! (%.format (%.nat arity) " " (synthesis.%synthesis body)))]
-    (case [arity body]
+    (when [arity body]
       (^.or [0 _]
             [1 _])
       body
@@ -833,9 +833,9 @@
       [2 {synthesis.#Control {synthesis.#Branch {synthesis.#Let _ 2 (synthesis.tuple (list _ hidden))}}}]
       hidden
       
-      [_ {synthesis.#Control {synthesis.#Branch {synthesis.#Case _ path}}}]
+      [_ {synthesis.#Control {synthesis.#Branch {synthesis.#When _ path}}}]
       (loop (again [path (is Path path)])
-        (case path
+        (when path
           {synthesis.#Seq _ next}
           (again next)
           
@@ -852,7 +852,7 @@
   (-> (-> Synthesis Synthesis)
       (-> Path Path))
   (function (again it)
-    (case it
+    (when it
       (^.or {synthesis.#Pop}
             {synthesis.#Access _})
       it
@@ -884,13 +884,13 @@
 
 (def .public (without_fake_parameter it)
   (-> Synthesis Synthesis)
-  (case it
+  (when it
     {synthesis.#Simple _}
     it
     
     {synthesis.#Structure it}
     {synthesis.#Structure
-     (case it
+     (when it
        {complex.#Variant it}
        {complex.#Variant (revised complex.#value without_fake_parameter it)}
 
@@ -899,10 +899,10 @@
     
     {synthesis.#Reference it}
     {synthesis.#Reference
-     (case it
+     (when it
        {//////reference.#Variable it}
        {//////reference.#Variable
-        (case it
+        (when it
           {//////variable.#Local it}
           {//////variable.#Local (-- it)}
           
@@ -914,10 +914,10 @@
     
     {synthesis.#Control it}
     {synthesis.#Control
-     (case it
+     (when it
        {synthesis.#Branch it}
        {synthesis.#Branch
-        (case it
+        (when it
           {synthesis.#Exec before after}
           {synthesis.#Exec (without_fake_parameter before)
                            (without_fake_parameter after)}
@@ -936,13 +936,13 @@
           {synthesis.#Get members
                           (without_fake_parameter record)}
           
-          {synthesis.#Case value path}
-          {synthesis.#Case (without_fake_parameter value)
+          {synthesis.#When value path}
+          {synthesis.#When (without_fake_parameter value)
                            (without_fake_parameter#path without_fake_parameter path)})}
        
        {synthesis.#Loop it}
        {synthesis.#Loop
-        (case it
+        (when it
           {synthesis.#Scope [synthesis.#start start
                              synthesis.#inits inits
                              synthesis.#iteration iteration]}
@@ -955,7 +955,7 @@
        
        {synthesis.#Function it}
        {synthesis.#Function
-        (case it
+        (when it
           {synthesis.#Abstraction [synthesis.#environment environment
                                    synthesis.#arity arity
                                    synthesis.#body body]}
@@ -995,7 +995,7 @@
                              strict_fp? annotations vars
                              self_name arguments returnT exceptionsT
                              (<| (..hidden_method_body arity)
-                                 (case arity
+                                 (when arity
                                    0 (without_fake_parameter body)
                                    _ body))]]))))
 
@@ -1003,7 +1003,7 @@
   (-> (-> Synthesis Synthesis)
       (-> Path Path))
   (function (again path)
-    (case path
+    (when path
       (synthesis.path/then bodyS)
       (synthesis.path/then (normalize bodyS))
 
@@ -1039,7 +1039,7 @@
 (def (normalize_method_body mapping)
   (-> Mapping Synthesis Synthesis)
   (function (again body)
-    (case body
+    (when body
       (^.with_template [<tag>]
         [<tag>
          body])
@@ -1058,8 +1058,8 @@
           (maybe.else var)
           synthesis.variable)
 
-      (synthesis.branch/case [inputS pathS])
-      (synthesis.branch/case [(again inputS) (normalize_path again pathS)])
+      (synthesis.branch/when [inputS pathS])
+      (synthesis.branch/when [(again inputS) (normalize_path again pathS)])
 
       (synthesis.branch/exec [this that])
       (synthesis.branch/exec [(again this) (again that)])
@@ -1081,7 +1081,7 @@
 
       (synthesis.function/abstraction [environment arity bodyS])
       (synthesis.function/abstraction [(list#each (function (_ captured)
-                                                    (case captured
+                                                    (when captured
                                                       (synthesis.variable var)
                                                       (|> mapping
                                                           (dictionary.value captured)
@@ -1116,7 +1116,7 @@
         inputs! (|> inputsTG
                     list.enumeration
                     (list#each (function (_ [register [type term]])
-                                 (let [then! (case (type.primitive? type)
+                                 (let [then! (when (type.primitive? type)
                                                {.#Right type}
                                                (///value.unwrap type)
                                                
@@ -1161,14 +1161,14 @@
 
 (def (returnG returnT)
   (-> (Type Return) (Bytecode Any))
-  (case (type.void? returnT)
+  (when (type.void? returnT)
     {.#Right returnT}
     _.return
 
     {.#Left returnT}
-    (case (type.primitive? returnT)
+    (when (type.primitive? returnT)
       {.#Left returnT}
-      (case (type.class? returnT)
+      (when (type.class? returnT)
         {.#Some class_name}
         (all _.composite
              (_.checkcast returnT)
@@ -1221,7 +1221,7 @@
 
 (def (prepare_argument lux_register argumentT jvm_register)
   (-> Register (Type Value) Register [Register (Bytecode Any)])
-  (case (type.primitive? argumentT)
+  (when (type.primitive? argumentT)
     {.#Left argumentT}
     [(n.+ 1 jvm_register)
      (if (n.= lux_register jvm_register)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/lua/common.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/lua/common.lux
index 8fdfccda4..80882cbbd 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/lua/common.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/lua/common.lux
@@ -34,7 +34,7 @@
      ["[1][0]" primitive]
      ["[1][0]" structure]
      ["[1][0]" reference]
-     ["[1][0]" case]
+     ["[1][0]" when]
      ["[1][0]" loop]
      ["[1][0]" function]]]
    [//
@@ -50,7 +50,7 @@
          (-> Text (Generator s))]
         Handler))
   (function (_ extension_name phase archive input)
-    (case (<s>.result parser input)
+    (when (<s>.result parser input)
       {try.#Success input'}
       (handler extension_name phase archive input')
 
@@ -63,7 +63,7 @@
 
 (def .public (statement expression archive synthesis)
   Phase!
-  (case synthesis
+  (when synthesis
     ... TODO: Get rid of this ASAP
     {synthesis.#Extension "lux syntax char case!" parameters}
     (do /////.monad
@@ -88,17 +88,17 @@
     ([synthesis.#Reference]
      [synthesis.#Extension])
 
-    (synthesis.branch/case case)
-    (//case.case! statement expression archive case)
+    (synthesis.branch/when when)
+    (//when.when! statement expression archive when)
 
     (synthesis.branch/exec it)
-    (//case.exec! statement expression archive it)
+    (//when.exec! statement expression archive it)
 
     (synthesis.branch/let let)
-    (//case.let! statement expression archive let)
+    (//when.let! statement expression archive let)
 
     (synthesis.branch/if if)
-    (//case.if! statement expression archive if)
+    (//when.if! statement expression archive if)
 
     (synthesis.loop/scope scope)
     (do /////.monad
@@ -123,7 +123,7 @@
              (function (_ extension_name phase archive [input else conditionals])
                (|> conditionals
                    (list#each (function (_ [chars branch])
-                                {synthesis.#Seq (case chars
+                                {synthesis.#Seq (when chars
                                                   {.#End}
                                                   {synthesis.#Pop}
                                                   
@@ -139,7 +139,7 @@
                                {synthesis.#Alt pre post})
                              {synthesis.#Then else})
                    [input]
-                   (//case.case! statement phase archive)
+                   (//when.when! statement phase archive)
                    (at /////.monad each (|>> (as Expression)))))]))
 
 (def lux_procs
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/lua/host.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/lua/host.lux
index 603d2efb2..5072f1488 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/lua/host.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/lua/host.lux
@@ -180,7 +180,7 @@
                               (list.repeated (.nat arity) []))]
         (in (<| (_.closure g!inputs)
                 _.return
-                (case (.nat arity)
+                (when (.nat arity)
                   0 (_.apply (list //runtime.unit) abstractionG)
                   1 (_.apply g!inputs abstractionG)
                   _ (_.apply (list (_.array g!inputs)) abstractionG))))))]))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/php/common.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/php/common.lux
index 8fcabe6e4..00c99a594 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/php/common.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/php/common.lux
@@ -31,7 +31,7 @@
     ["[0]" reference]
     ["//" php
      ["[1][0]" runtime (.only Operation Phase Handler Bundle Generator)]
-     ["[1][0]" case]]]
+     ["[1][0]" when]]]
    [//
     ["[0]" synthesis (.only %synthesis)
      ["<s>" \\parser (.only Parser)]]
@@ -45,7 +45,7 @@
          (-> Text (Generator s))]
         Handler))
   (function (_ extension_name phase archive input)
-    (case (<s>.result parser input)
+    (when (<s>.result parser input)
       {try.#Success input'}
       (handler extension_name phase archive input')
 
@@ -84,8 +84,8 @@
                                                            branchG])))
                                                 conditionals))
                   .let [foreigns (|> conditionals
-                                     (list#each (|>> product.right synthesis.path/then //case.dependencies))
-                                     (list.partial (//case.dependencies (synthesis.path/then else)))
+                                     (list#each (|>> product.right synthesis.path/then //when.dependencies))
+                                     (list.partial (//when.dependencies (synthesis.path/then else)))
                                      list.together
                                      (set.of_list _.hash)
                                      set.list)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/python/common.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/python/common.lux
index b4a6a8f0c..5bb154a47 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/python/common.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/python/common.lux
@@ -36,7 +36,7 @@
      ["[1][0]" structure]
      ["[1][0]" reference]
      ["[1][0]" function]
-     ["[1][0]" case]
+     ["[1][0]" when]
      ["[1][0]" loop]]]
    [//
     [analysis (.only)]
@@ -48,7 +48,7 @@
 
 (def .public (statement expression archive synthesis)
   Phase!
-  (case synthesis
+  (when synthesis
     ... TODO: Get rid of this ASAP
     {synthesis.#Extension "lux syntax char case!" parameters}
     (do /////.monad
@@ -73,15 +73,15 @@
     ([synthesis.#Reference]
      [synthesis.#Extension])
 
-    (synthesis.branch/case case)
-    (//case.case! false statement expression archive case)
+    (synthesis.branch/when when)
+    (//when.when! false statement expression archive when)
 
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (<generator> statement expression archive value)])
-    ([synthesis.branch/exec //case.exec!]
-     [synthesis.branch/let //case.let!]
-     [synthesis.branch/if //case.if!]
+    ([synthesis.branch/exec //when.exec!]
+     [synthesis.branch/let //when.let!]
+     [synthesis.branch/if //when.if!]
      [synthesis.loop/scope //loop.scope!]
      [synthesis.loop/again //loop.again!])
 
@@ -95,7 +95,7 @@
          (-> Text (Generator s))]
         Handler))
   (function (_ extension_name phase archive input)
-    (case (<synthesis>.result parser input)
+    (when (<synthesis>.result parser input)
       {try.#Success input'}
       (handler extension_name phase archive input')
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/python/host.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/python/host.lux
index 3354e69db..fde1ab399 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/python/host.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/python/host.lux
@@ -140,7 +140,7 @@
          g!inputs (monad.each ! (function (_ _) (variable "input"))
                               (list.repeated (.nat arity) []))]
         (in (_.lambda g!inputs
-                      (case (.nat arity)
+                      (when (.nat arity)
                         0 (_.apply (list //runtime.unit) abstractionG)
                         1 (_.apply g!inputs abstractionG)
                         _ (_.apply (list (_.list g!inputs)) abstractionG))))))]))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/r/common.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/r/common.lux
index b2dbae1f3..faab4946a 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/r/common.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/r/common.lux
@@ -31,7 +31,7 @@
     ["[0]" reference]
     ["//" r
      ["[1][0]" runtime (.only Operation Phase Handler Bundle Generator)]
-     ["[1][0]" case]]]
+     ["[1][0]" when]]]
    [//
     ["[0]" synthesis (.only %synthesis)
      ["<s>" \\parser (.only Parser)]]
@@ -45,7 +45,7 @@
          (-> Text (Generator s))]
         Handler))
   (function (_ extension_name phase archive input)
-    (case (<s>.result parser input)
+    (when (<s>.result parser input)
       {try.#Success input'}
       (handler extension_name phase archive input')
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/ruby/common.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/ruby/common.lux
index dca8af12f..9c136ef38 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/ruby/common.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/ruby/common.lux
@@ -35,7 +35,7 @@
      ["[1][0]" structure]
      ["[1][0]" reference]
      ["[1][0]" function]
-     ["[1][0]" case]
+     ["[1][0]" when]
      ["[1][0]" loop]]]
    [//
     ["[0]" generation]
@@ -50,7 +50,7 @@
          (-> Text (Generator s))]
         Handler))
   (function (_ extension_name phase archive input)
-    (case (<s>.result parser input)
+    (when (<s>.result parser input)
       {try.#Success input'}
       (handler extension_name phase archive input')
 
@@ -59,7 +59,7 @@
 
 (def .public (statement expression archive synthesis)
   Phase!
-  (case synthesis
+  (when synthesis
     ... TODO: Get rid of this ASAP
     {synthesis.#Extension "lux syntax char case!" parameters}
     (do /////.monad
@@ -85,15 +85,15 @@
     ([synthesis.#Reference]
      [synthesis.#Extension])
 
-    (synthesis.branch/case case)
-    (//case.case! false statement expression archive case)
+    (synthesis.branch/when when)
+    (//when.when! false statement expression archive when)
 
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (<generator> statement expression archive value)])
-    ([synthesis.branch/exec //case.exec!]
-     [synthesis.branch/let //case.let!]
-     [synthesis.branch/if //case.if!]
+    ([synthesis.branch/exec //when.exec!]
+     [synthesis.branch/let //when.let!]
+     [synthesis.branch/if //when.if!]
      [synthesis.loop/scope //loop.scope!]
      [synthesis.loop/again //loop.again!])
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/scheme/common.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/scheme/common.lux
index 2b8bbcba8..9eec19a4a 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/scheme/common.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/extension/generation/scheme/common.lux
@@ -31,7 +31,7 @@
     ["[0]" reference]
     ["//" scheme
      ["[1][0]" runtime (.only Operation Phase Handler Bundle Generator)]
-     ["[1][0]" case]]]
+     ["[1][0]" when]]]
    [//
     ["[0]" generation]
     ["[0]" synthesis (.only %synthesis)
@@ -45,7 +45,7 @@
          (-> Text (Generator s))]
         Handler))
   (function (_ extension_name phase archive input)
-    (case (<s>.result parser input)
+    (when (<s>.result parser input)
       {try.#Success input'}
       (handler extension_name phase archive input')
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp.lux
index 1168d5b8b..0f1867ff7 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp.lux
@@ -11,7 +11,7 @@
   ["[1][0]" primitive]
   ["[1][0]" structure]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" loop]
   ["[1][0]" function]
   ["/[1]" //
@@ -28,7 +28,7 @@
 
 (def .public (generate archive synthesis)
   Phase
-  (case synthesis
+  (when synthesis
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (//////phase#in (<generator> value))])
@@ -45,12 +45,12 @@
        (<generator> generate archive value)])
     ([////synthesis.variant /structure.variant]
      [////synthesis.tuple /structure.tuple]
-     [////synthesis.branch/let /case.let]
-     [////synthesis.branch/if /case.if]
-     [////synthesis.branch/get /case.get]
+     [////synthesis.branch/let /when.let]
+     [////synthesis.branch/if /when.if]
+     [////synthesis.branch/get /when.get]
      [////synthesis.function/apply /function.apply]
 
-     [////synthesis.branch/case /case.case]
+     [////synthesis.branch/when /when.when]
      [////synthesis.loop/scope /loop.scope]
      [////synthesis.loop/again /loop.again]
      [////synthesis.function/abstraction /function.function])
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/function.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/function.lux
index 6b6fd617d..5a9e65883 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/function.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/function.lux
@@ -17,7 +17,7 @@
  ["[0]" //
   ["[1][0]" runtime (.only Operation Phase Generator)]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["//[1]" ///
@@ -43,7 +43,7 @@
 
 (def (with_closure inits function_definition)
   (-> (List (Expression Any)) (Expression Any) (Operation (Expression Any)))
-  (case inits
+  (when inits
     {.#End}
     (at ///////phase.monad in function_definition)
 
@@ -57,7 +57,7 @@
                     (_.funcall/+ [(_.function/1 @closure) inits]))))))
 
 (def input
-  (|>> ++ //case.register))
+  (|>> ++ //when.register))
 
 (def .public (function expression archive [environment arity bodyS])
   (Generator (Abstraction Synthesis))
@@ -73,7 +73,7 @@
            arityG (|> arity .int _.int)
            @num_args (_.var "num_args")
            @self (_.var (///reference.artifact function_name))
-           initialize_self! [(//case.register 0) (_.function/1 @self)]
+           initialize_self! [(//when.register 0) (_.function/1 @self)]
            initialize! [(|> (list.indices arity)
                             (list#each ..input)
                             _.args)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/loop.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/loop.lux
index ad1f110de..d2dcb8802 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/loop.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/loop.lux
@@ -17,12 +17,12 @@
      ["_" common_lisp (.only Expression)]]]]]
  ["[0]" //
   [runtime (.only Operation Phase Generator)]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["/[1]" //
     [synthesis
-     ["[0]" case]]
+     ["[0]" when]]
     ["/[1]" //
      ["[0]"synthesis (.only Scope Synthesis)]
      ["[1][0]" generation]
@@ -35,7 +35,7 @@
 
 (def .public (scope expression archive [start initsS+ bodyS])
   (Generator (Scope Synthesis))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (expression archive bodyS)
@@ -52,7 +52,7 @@
       (in (_.let (|> initsG+
                      list.enumeration
                      (list#each (function (_ [idx init])
-                                  [(|> idx (n.+ start) //case.register)
+                                  [(|> idx (n.+ start) //when.register)
                                    init]))
                      (list.partial [@output _.nil]))
             (list (_.tagbody (list @scope
@@ -66,7 +66,7 @@
      argsO+ (monad.each ! (expression archive) argsS+)
      .let [bindings (|> argsO+
                         list.enumeration
-                        (list#each (|>> product.left (n.+ offset) //case.register))
+                        (list#each (|>> product.left (n.+ offset) //when.register))
                         _.args)]]
     (in (_.progn (list (_.multiple_value_setq bindings (_.values/* argsO+))
                        (_.go tag))))))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/runtime.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/runtime.lux
index 77f1e5cfd..9294d4335 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/runtime.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/runtime.lux
@@ -110,7 +110,7 @@
       (macro.with_symbols [g!_]
         (let [runtime (code.local (///reference.artifact [..module_id runtime_id]))
               runtime_name (` (_.var (, (code.text (%.code runtime)))))]
-          (case declaration
+          (when declaration
             {.#Left name}
             (let [g!name (code.local name)
                   code_nameC (code.local (format "@" name))]
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/structure.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/structure.lux
index af4d6023b..c4aabc6f2 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/structure.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/structure.lux
@@ -17,7 +17,7 @@
 
 (def .public (tuple expression archive elemsS+)
   (Generator (Tuple Synthesis))
-  (case elemsS+
+  (when elemsS+
     {.#End}
     (///////phase#in (//primitive.text /////synthesis.unit))
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/case.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/when.lux
index cd5ef69ad..731102b94 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/case.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/common_lisp/when.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except case let if)
+  [lux (.except when let if)
    [abstract
     ["[0]" monad (.only do)]]
    [data
@@ -25,7 +25,7 @@
    ["[1][0]" reference]
    ["/[1]" //
     ["[1][0]" synthesis
-     ["[1]/[0]" case]]
+     ["[1]/[0]" when]]
     ["/[1]" //
      ["[1][0]" synthesis (.only Member Synthesis Path)]
      ["[1][0]" generation]
@@ -65,7 +65,7 @@
   (do ///////phase.monad
     [valueG (expression archive valueS)]
     (in (list#mix (function (_ side source)
-                    (.let [method (.case side
+                    (.let [method (.when side
                                     (^.with_template [<side> <accessor>]
                                       [(<side> lefts)
                                        (<accessor> (_.int (.int lefts)))])
@@ -113,11 +113,11 @@
          (list.partial (_.setq @temp (|> idx <prep> .int _.int (//runtime.sum//get @variant <flag>)))
                        (.if simple?
                          (_.when <failure_condition>
-                                 (_.go @fail))
+                           (_.go @fail))
                          (_.if <failure_condition>
                            (_.go @fail)
                            (..push! @temp)))
-                       (.case next!
+                       (.when next!
                          {.#Some next!}
                          (list next!)
                          
@@ -140,7 +140,7 @@
 (def (pattern_matching' expression archive)
   (Generator [Var/1 _.Tag _.Tag Path])
   (function (again [$output @done @fail pathP])
-    (.case pathP
+    (.when pathP
       (/////synthesis.path/then bodyS)
       (at ///////phase.monad each
           (function (_ outputV)
@@ -157,7 +157,7 @@
       {/////synthesis.#Bit_Fork when thenP elseP}
       (do [! ///////phase.monad]
         [then! (again [$output @done @fail thenP])
-         else! (.case elseP
+         else! (.when elseP
                  {.#Some elseP}
                  (again [$output @done @fail elseP])
 
@@ -210,7 +210,7 @@
        [/////synthesis.member/right //runtime.tuple//right])
 
       (/////synthesis.!multi_pop nextP)
-      (.let [[extra_pops nextP'] (////synthesis/case.count_pops nextP)]
+      (.let [[extra_pops nextP'] (////synthesis/when.count_pops nextP)]
         (do ///////phase.monad
           [next! (again [$output @done @fail nextP'])]
           (///////phase#in (_.progn (list (..multi_pop! (n.+ 2 extra_pops))
@@ -218,7 +218,7 @@
 
       (/////synthesis.path/alt preP postP)
       (do [! ///////phase.monad]
-        [@otherwise (at ! each (|>> %.nat (format "lux_case_otherwise") _.tag) /////generation.next)
+        [@otherwise (at ! each (|>> %.nat (format "lux_when_otherwise") _.tag) /////generation.next)
          pre! (again [$output @done @otherwise preP])
          post! (again [$output @done @fail postP])]
         (in (..alternation @otherwise pre! post!)))
@@ -232,24 +232,24 @@
 (def (pattern_matching $output expression archive pathP)
   (-> Var/1 (Generator Path))
   (do [! ///////phase.monad]
-    [@done (at ! each (|>> %.nat (format "lux_case_done") _.tag) /////generation.next)
-     @fail (at ! each (|>> %.nat (format "lux_case_fail") _.tag) /////generation.next)
+    [@done (at ! each (|>> %.nat (format "lux_when_done") _.tag) /////generation.next)
+     @fail (at ! each (|>> %.nat (format "lux_when_fail") _.tag) /////generation.next)
      pattern_matching! (pattern_matching' expression archive [$output @done @fail pathP])]
     (in (_.tagbody
          (list pattern_matching!
                @fail
-               (_.error/1 (_.string ////synthesis/case.pattern_matching_error))
+               (_.error/1 (_.string ////synthesis/when.pattern_matching_error))
                @done)))))
 
-(def .public (case expression archive [valueS pathP])
+(def .public (when expression archive [valueS pathP])
   (Generator [Synthesis Path])
   (do [! ///////phase.monad]
     [initG (expression archive valueS)
-     $output (at ! each (|>> %.nat (format "lux_case_output") _.var) /////generation.next)
+     $output (at ! each (|>> %.nat (format "lux_when_output") _.var) /////generation.next)
      pattern_matching! (pattern_matching $output expression archive pathP)
      .let [storage (|> pathP
-                       ////synthesis/case.storage
-                       (the ////synthesis/case.#bindings)
+                       ////synthesis/when.storage
+                       (the ////synthesis/when.#bindings)
                        set.list
                        (list#each (function (_ register)
                                     [(..register register)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/extension.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/extension.lux
index 9d2c7e1db..3566da9bf 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/extension.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/extension.lux
@@ -39,7 +39,7 @@
                                (generation.Handler (, g!anchor) (, g!expression) (, g!declaration))))
                          (function ((, g!_) (, g!extension))
                            (function ((, g!_) (, g!name) (, g!phase) (, g!archive) (, g!inputs))
-                             (case (, g!inputs)
+                             (when (, g!inputs)
                                (list (,* g!input+))
                                (do ///.monad
                                  [(,* (|> g!input+
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js.lux
index 864edbf16..009b99257 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js.lux
@@ -15,7 +15,7 @@
   ["[1][0]" primitive]
   ["[1][0]" structure]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" loop]
   ["[1][0]" function]
   ["/[1]" //
@@ -37,7 +37,7 @@
 
 (def (expression archive synthesis)
   Phase
-  (case synthesis
+  (when synthesis
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (//////phase#in (<generator> value))])
@@ -55,20 +55,20 @@
     {synthesis.#Reference value}
     (//reference.reference /reference.system archive value)
 
-    (synthesis.branch/case case)
-    (/case.case ///extension/common.statement expression archive case)
+    (synthesis.branch/when when)
+    (/when.when ///extension/common.statement expression archive when)
 
     (synthesis.branch/exec it)
-    (/case.exec expression archive it)
+    (/when.exec expression archive it)
 
     (synthesis.branch/let let)
-    (/case.let expression archive let)
+    (/when.let expression archive let)
 
     (synthesis.branch/if if)
-    (/case.if expression archive if)
+    (/when.if expression archive if)
 
     (synthesis.branch/get get)
-    (/case.get expression archive get)
+    (/when.get expression archive get)
 
     (synthesis.loop/scope scope)
     (/loop.scope ///extension/common.statement expression archive scope)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/function.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/function.lux
index 5d5cf5e13..f0bb48d3d 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/function.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/function.lux
@@ -15,7 +15,7 @@
  ["[0]" //
   ["[1][0]" runtime (.only Operation Phase Phase! Generator)]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["//[1]" ///
@@ -47,7 +47,7 @@
 
 (def (with_closure @self inits body!)
   (-> Var (List Expression) Statement [Statement Expression])
-  (case inits
+  (when inits
     {.#End}
     [(_.function_definition @self (list) body!)
      @self]
@@ -63,7 +63,7 @@
   (_.var "curried"))
 
 (def input
-  (|>> ++ //case.register))
+  (|>> ++ //when.register))
 
 (def @@arguments
   (_.var "arguments"))
@@ -88,7 +88,7 @@
            @self (_.var (///reference.artifact function_name))
            apply_poly (.function (_ args func)
                         (|> func (_.do "apply" (list _.null args))))
-           initialize_self! (_.define (//case.register 0) @self)
+           initialize_self! (_.define (//when.register 0) @self)
            initialize! (list#mix (.function (_ post pre!)
                                    (all _.then
                                         pre!
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/loop.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/loop.lux
index bac543584..c475281e4 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/loop.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/loop.lux
@@ -17,7 +17,7 @@
      ["_" js (.only Computation Var Expression Statement)]]]]]
  ["[0]" //
   [runtime (.only Operation Phase Phase! Generator Generator!)]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["///[1]" ////
    [synthesis (.only Scope Synthesis)]
    ["[1][0]" generation]
@@ -36,12 +36,12 @@
 
 (def (setup $iteration initial? offset bindings body)
   (-> Var Bit Register (List Expression) Statement Statement)
-  (case bindings
+  (when bindings
     (list)
     body
 
     (list binding)
-    (let [$binding (//case.register offset)]
+    (let [$binding (//when.register offset)]
       (all _.then
            (if initial?
              (_.define $binding binding)
@@ -53,7 +53,7 @@
     (|> bindings
         list.enumeration
         (list#each (function (_ [register _])
-                     (let [variable (//case.register (n.+ offset register))]
+                     (let [variable (//when.register (n.+ offset register))]
                        (if initial?
                          (_.define variable (_.at (_.i32 (.int register)) $iteration))
                          (_.set variable (_.at (_.i32 (.int register)) $iteration))))))
@@ -63,7 +63,7 @@
 
 (def .public (scope! statement expression archive [start initsS+ bodyS])
   (Generator! (Scope Synthesis))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (statement expression archive bodyS)
@@ -85,7 +85,7 @@
 
 (def .public (scope statement expression archive [start initsS+ bodyS])
   (-> Phase! (Generator (Scope Synthesis)))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (expression archive bodyS)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/runtime.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/runtime.lux
index 437f6624d..73a240682 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/runtime.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/runtime.lux
@@ -101,7 +101,7 @@
               code <code>.any])
     (macro.with_symbols [g!_ runtime]
       (let [runtime_name (` (_.var (, (code.text (%.code runtime)))))]
-        (case declaration
+        (when declaration
           {.#Left name}
           (let [g!name (code.local name)]
             (in (list (` (def .public (, g!name)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/structure.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/structure.lux
index e5a492e37..ee1ae1a03 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/structure.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/structure.lux
@@ -18,7 +18,7 @@
 
 (def .public (tuple generate archive elemsS+)
   (Generator (Tuple Synthesis))
-  (case elemsS+
+  (when elemsS+
     {.#End}
     (///////phase#in //runtime.unit)
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/case.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/when.lux
index f8b30c1f9..7487beb55 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/case.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/js/when.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except case exec let if)
+  [lux (.except when exec let if)
    [abstract
     ["[0]" monad (.only do)]]
    [control
@@ -25,7 +25,7 @@
    ["[1][0]" reference]
    ["/[1]" //
     ["[1][0]" synthesis
-     ["[1]/[0]" case]]
+     ["[1]/[0]" when]]
     ["/[1]" //
      ["[1][0]" synthesis (.only Synthesis Path)
       [access
@@ -158,7 +158,7 @@
                                            (|> idx .int _.i32)))
           (.if simple?
             (_.when (_.= _.null @temp)
-                    ..fail_pm!)
+              ..fail_pm!)
             (_.if (_.= _.null @temp)
               ..fail_pm!
               (push_cursor! @temp)))))]
@@ -181,7 +181,7 @@
 (def (optimized_pattern_matching again pathP)
   (-> (-> Path (Operation Statement))
       (-> Path (Operation (Maybe Statement))))
-  (.case pathP
+  (.when pathP
     (^.with_template [<simple> <choice>]
       [(<simple> idx nextP)
        (|> nextP
@@ -224,7 +224,7 @@
                        then!)}))
 
     (/////synthesis.!multi_pop nextP)
-    (.let [[extra_pops nextP'] (////synthesis/case.count_pops nextP)]
+    (.let [[extra_pops nextP'] (////synthesis/when.count_pops nextP)]
       (do ///////phase.monad
         [next! (again nextP')]
         (in {.#Some (all _.then
@@ -240,12 +240,12 @@
   (function (again pathP)
     (do ///////phase.monad
       [outcome (optimized_pattern_matching again pathP)]
-      (.case outcome
+      (.when outcome
         {.#Some outcome}
         (in outcome)
 
         {.#None}
-        (.case pathP
+        (.when pathP
           {/////synthesis.#Then bodyS}
           (statement expression archive bodyS)
 
@@ -258,7 +258,7 @@
           {/////synthesis.#Bit_Fork when thenP elseP}
           (do [! ///////phase.monad]
             [then! (again thenP)
-             else! (.case elseP
+             else! (.when elseP
                      {.#Some elseP}
                      (again elseP)
 
@@ -326,9 +326,9 @@
     (in (all _.then
              (_.do_while (_.boolean false)
                          pattern_matching!)
-             (_.throw (_.string ////synthesis/case.pattern_matching_error))))))
+             (_.throw (_.string ////synthesis/when.pattern_matching_error))))))
 
-(def .public (case! statement expression archive [valueS pathP])
+(def .public (when! statement expression archive [valueS pathP])
   (Generator! [Synthesis Path])
   (do ///////phase.monad
     [stack_init (expression archive valueS)
@@ -339,8 +339,8 @@
              (_.define @savepoint (_.array (list)))
              pattern_matching!))))
 
-(def .public (case statement expression archive [valueS pathP])
+(def .public (when statement expression archive [valueS pathP])
   (-> Phase! (Generator [Synthesis Path]))
   (do ///////phase.monad
-    [pattern_matching! (..case! statement expression archive [valueS pathP])]
+    [pattern_matching! (..when! statement expression archive [valueS pathP])]
     (in (_.apply (_.closure (list) pattern_matching!) (list)))))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm.lux
index b1fa42f27..0b9ec3dba 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm.lux
@@ -12,7 +12,7 @@
   ["[1][0]" structure]
   ["[1][0]" reference]
   ["[1][0]" function]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" loop]
   ["//[1]" ///
    ["[1][0]" extension]
@@ -24,7 +24,7 @@
 
 (def .public (generate archive synthesis)
   Phase
-  (case synthesis
+  (when synthesis
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (///#in (<generator> value))])
@@ -40,27 +40,27 @@
     (/structure.tuple generate archive members)
 
     {synthesis.#Reference reference}
-    (case reference
+    (when reference
       {reference.#Variable variable}
       (/reference.variable archive variable)
       
       {reference.#Constant constant}
       (/reference.constant archive constant))
 
-    (synthesis.branch/case [valueS pathS])
-    (/case.case generate archive [valueS pathS])
+    (synthesis.branch/when [valueS pathS])
+    (/when.when generate archive [valueS pathS])
 
     (synthesis.branch/exec [this that])
-    (/case.exec generate archive [this that])
+    (/when.exec generate archive [this that])
 
     (synthesis.branch/let [inputS register bodyS])
-    (/case.let generate archive [inputS register bodyS])
+    (/when.let generate archive [inputS register bodyS])
 
     (synthesis.branch/if [conditionS thenS elseS])
-    (/case.if generate archive [conditionS thenS elseS])
+    (/when.if generate archive [conditionS thenS elseS])
 
     (synthesis.branch/get [path recordS])
-    (/case.get generate archive [path recordS])
+    (/when.get generate archive [path recordS])
 
     (synthesis.loop/scope scope)
     (/loop.scope generate archive scope)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/debug.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/debug.lux
index b983c3b7d..51ae831e0 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/debug.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/debug.lux
@@ -23,7 +23,7 @@
                  [file (is (IO (Try (File IO)))
                            (file.get_file io.monad file.default file_path))]
                  (at file over_write bytecode))]
-      (in (case outcome
+      (in (when outcome
             {try.#Success definition}
             file_path
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/function.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/function.lux
index b150e4536..c6b9dac3a 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/function.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/function.lux
@@ -170,12 +170,12 @@
 
 (def .public (apply generate archive [abstractionS inputsS])
   (Generator Apply)
-  (case abstractionS
+  (when abstractionS
     (synthesis.constant $abstraction)
     (do [! phase.monad]
       [[@definition |abstraction|] (generation.definition archive $abstraction)
        .let [actual_arity (list.size inputsS)]]
-      (case |abstraction|
+      (when |abstraction|
         {.#Some [_ {.#Some [expected_arity @abstraction]}]}
         (cond (n.< expected_arity actual_arity)
               (apply/? generate archive [abstractionS inputsS])
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/function/method/apply.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/function/method/apply.lux
index 74a1dac76..ae502cbee 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/function/method/apply.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/function/method/apply.lux
@@ -87,7 +87,7 @@
     (method.method //.modifier ////runtime.apply::name
                    false (////runtime.apply::type apply_arity)
                    (list)
-                   {.#Some (case num_partials
+                   {.#Some (when num_partials
                              0 (all _.composite
                                     ////reference.this
                                     (..inputs ..this_offset apply_arity)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/host.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/host.lux
index 270fb31ab..973ab7cad 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/host.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/host.lux
@@ -86,11 +86,11 @@
 
 (def (class_value class_name class)
   (-> Text (java/lang/Class java/lang/Object) (Try Any))
-  (case (java/lang/Class::getField //value.field class)
+  (when (java/lang/Class::getField //value.field class)
     {try.#Success field}
-    (case (java/lang/reflect/Field::get {.#None} field)
+    (when (java/lang/reflect/Field::get {.#None} field)
       {try.#Success ?value}
-      (case ?value
+      (when ?value
         {.#Some value}
         {try.#Success value}
         
@@ -109,7 +109,7 @@
 (def (evaluate! library loader eval_class [@it valueG])
   (-> Library java/lang/ClassLoader Text [(Maybe unit.ID) (Bytecode Any)] (Try [Any Definition]))
   (let [bytecode_name (text.replaced class_path_separator .module_separator eval_class)
-        :value: (case @it
+        :value: (when @it
                   {.#Some @it}
                   (type.class (//runtime.class_name @it) (list))
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/loop.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/loop.lux
index d7b73995e..495882117 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/loop.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/loop.lux
@@ -29,7 +29,7 @@
 
 (def (invariant? register changeS)
   (-> Register Synthesis Bit)
-  (case changeS
+  (when changeS
     (synthesis.variable/local var)
     (n.= register var)
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/primitive.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/primitive.lux
index ad5a79db9..5c9677bb7 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/primitive.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/primitive.lux
@@ -34,7 +34,7 @@
 
 (def .public (i64 value)
   (-> (I64 Any) (Bytecode Any))
-  (case (.int value)
+  (when (.int value)
     (^.with_template [<int> <instruction>]
       [<int>
        (do _.monad
@@ -58,7 +58,7 @@
      [+5 _.iconst_5])
 
     value
-    (case (signed.s1 value)
+    (when (signed.s1 value)
       {try.#Success value}
       (do _.monad
         [_ (_.bipush value)
@@ -66,7 +66,7 @@
         ..wrap_i64)
 
       {try.#Failure _}
-      (case (signed.s2 value)
+      (when (signed.s2 value)
         {try.#Success value}
         (do _.monad
           [_ (_.sipush value)
@@ -91,7 +91,7 @@
 
 (def .public (f64 value)
   (-> Frac (Bytecode Any))
-  (case value
+  (when value
     (^.with_template [<int> <instruction>]
       [<int>
        (do _.monad
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/reference.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/reference.lux
index a6f209206..9f4a1c945 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/reference.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/reference.lux
@@ -53,7 +53,7 @@
 
 (def .public (variable archive variable)
   (-> Archive Variable (Operation (Bytecode Any)))
-  (case variable
+  (when variable
     {variable.#Local variable}
     (operation#in (_.aload variable))
     
@@ -65,7 +65,7 @@
   (do ////.monad
     [[@definition |abstraction|] (generation.definition archive name)
      .let [:definition: (type.class (//runtime.class_name @definition) (list))]]
-    (in (case |abstraction|
+    (in (when |abstraction|
           {.#Some [_ {.#Some [expected_arity @abstraction]}]}
           (let [:abstraction: (type.class (//runtime.class_name @abstraction) (list))]
             (_.getstatic :definition: //value.field :abstraction:))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/runtime.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/runtime.lux
index 385015373..2a0d2c994 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/runtime.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/runtime.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except Type Definition Label case false true try)
+  [lux (.except Type Definition Label when false true try)
    [abstract
     ["[0]" monad (.only do)]
     ["[0]" enum]]
@@ -289,13 +289,13 @@
                          (..set! ..stack_tail $tail)
                          _.areturn))}))
 
-(def case::name "case")
-(def case::type (type.method [(list) (list //type.variant //type.lefts //type.right?) //type.value (list)]))
-(def .public case (..procedure ..case::name ..case::type))
+(def when::name "when")
+(def when::type (type.method [(list) (list //type.variant //type.lefts //type.right?) //type.value (list)]))
+(def .public when (..procedure ..when::name ..when::type))
 
-(def case::method
-  (method.method ..modifier ..case::name
-                 .false ..case::type
+(def when::method
+  (method.method ..modifier ..when::name
+                 .false ..when::type
                  (list)
                  {.#Some
                   (do _.monad
@@ -560,7 +560,7 @@
                                ..pm_failure::method
 
                                ..push::method
-                               ..case::method
+                               ..when::method
                                left_projection::method
                                right_projection::method
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/structure.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/structure.lux
index 54958837b..1dfafd509 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/structure.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/structure.lux
@@ -31,7 +31,7 @@
 
 (def .public (tuple phase archive membersS)
   (Generator (Tuple Synthesis))
-  (case membersS
+  (when membersS
     {.#End}
     (at phase.monad in //runtime.unit)
 
@@ -57,19 +57,19 @@
 
 (def .public (lefts lefts)
   (-> Nat (Bytecode Any))
-  (case lefts
+  (when lefts
     0 _.iconst_0
     1 _.iconst_1
     2 _.iconst_2
     3 _.iconst_3
     4 _.iconst_4
     5 _.iconst_5
-    _ (case (signed.s1 (.int lefts))
+    _ (when (signed.s1 (.int lefts))
         {try.#Success value}
         (_.bipush value)
 
         {try.#Failure _}
-        (case (signed.s2 (.int lefts))
+        (when (signed.s2 (.int lefts))
           {try.#Success value}
           (_.sipush value)
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/case.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/when.lux
index f5d258fbb..767a48216 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/case.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/jvm/when.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except Type Label if let exec case int)
+  [lux (.except Type Label if let exec when int)
    [abstract
     ["[0]" monad (.only do)]]
    [control
@@ -42,7 +42,7 @@
 
 (def (pop_alt stack_depth)
   (-> Nat (Bytecode Any))
-  (.case stack_depth
+  (.when stack_depth
     0 (_#in [])
     1 _.pop
     2 _.pop2
@@ -76,7 +76,7 @@
   (all _.composite
        (_.checkcast //type.tuple)
        (..int lefts)
-       (.case lefts
+       (.when lefts
          0
          _.aaload
          
@@ -107,7 +107,7 @@
       (Operation (Bytecode Any)))
   (do phase.monad
     [then! (again thenP)
-     else! (.case elseP
+     else! (.when elseP
              {.#Some elseP}
              (again elseP)
 
@@ -161,7 +161,7 @@
 (def (path' stack_depth @else @end phase archive)
   (-> Nat Label Label (Generator Path))
   (function (again path)
-    (.case path
+    (.when path
       {synthesis.#Pop}
       (operation#in ..pop)
       
@@ -193,7 +193,7 @@
               (_.checkcast //type.variant)
               (//structure.lefts lefts)
               (//structure.right? right?)
-              //runtime.case
+              //runtime.when
               _.dup
               (_.ifnonnull @success)
               _.pop
@@ -312,7 +312,7 @@
                   record!
                   (list.reversed path)))))
 
-(def .public (case phase archive [valueS path])
+(def .public (when phase archive [valueS path])
   (Generator [Synthesis Path])
   (do phase.monad
     [@end //runtime.forge_label
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua.lux
index 2e27b6973..08fbc07cf 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua.lux
@@ -15,7 +15,7 @@
   ["[1][0]" primitive]
   ["[1][0]" structure]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" loop]
   ["[1][0]" function]
   ["/[1]" //
@@ -37,7 +37,7 @@
 
 (def (expression archive synthesis)
   Phase
-  (case synthesis
+  (when synthesis
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (//////phase#in (<generator> value))])
@@ -55,20 +55,20 @@
     {synthesis.#Reference value}
     (//reference.reference /reference.system archive value)
 
-    (synthesis.branch/case case)
-    (/case.case ///extension/common.statement expression archive case)
+    (synthesis.branch/when when)
+    (/when.when ///extension/common.statement expression archive when)
 
     (synthesis.branch/exec it)
-    (/case.exec expression archive it)
+    (/when.exec expression archive it)
 
     (synthesis.branch/let let)
-    (/case.let expression archive let)
+    (/when.let expression archive let)
 
     (synthesis.branch/if if)
-    (/case.if expression archive if)
+    (/when.if expression archive if)
 
     (synthesis.branch/get get)
-    (/case.get expression archive get)
+    (/when.get expression archive get)
 
     (synthesis.loop/scope scope)
     (/loop.scope ///extension/common.statement expression archive scope)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/function.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/function.lux
index 77f3d2caf..0e7b19de8 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/function.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/function.lux
@@ -15,7 +15,7 @@
  ["[0]" //
   ["[1][0]" runtime (.only Operation Phase Phase! Generator)]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["//[1]" ///
@@ -47,7 +47,7 @@
 
 (def (with_closure inits @self @args body!)
   (-> (List Expression) Var (List Var) Statement [Statement Expression])
-  (case inits
+  (when inits
     {.#End}
     [(_.function @self @args body!)
      @self]
@@ -62,7 +62,7 @@
        (_.apply inits @self)])))
 
 (def input
-  (|>> ++ //case.register))
+  (|>> ++ //when.register))
 
 (def (@scope function_name)
   (-> unit.ID Label)
@@ -84,7 +84,7 @@
            @num_args (_.var "num_args")
            @scope (..@scope function_name)
            @self (_.var (///reference.artifact function_name))
-           initialize_self! (_.local/1 (//case.register 0) @self)
+           initialize_self! (_.local/1 (//when.register 0) @self)
            initialize! (list#mix (.function (_ post pre!)
                                    (all _.then
                                         pre!
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/loop.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/loop.lux
index bef9f9893..f3532770a 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/loop.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/loop.lux
@@ -18,7 +18,7 @@
      ["_" lua (.only Var Expression Label Statement)]]]]]
  ["[0]" //
   [runtime (.only Operation Phase Phase! Generator Generator!)]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["//[1]" ///
@@ -42,7 +42,7 @@
   (-> Bit Register (List Expression) Bit Statement Statement)
   (let [variables (|> bindings
                       list.enumeration
-                      (list#each (|>> product.left (n.+ offset) //case.register)))]
+                      (list#each (|>> product.left (n.+ offset) //when.register)))]
     (if as_expression?
       body
       (all _.then
@@ -55,7 +55,7 @@
   ... (Generator! (Scope Synthesis))
   (-> Phase! Phase Archive Bit (Scope Synthesis)
       (Operation [(List Expression) Statement]))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (|> bodyS
@@ -77,7 +77,7 @@
 
 (def .public (scope statement expression archive [start initsS+ bodyS])
   (-> Phase! (Generator (Scope Synthesis)))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (expression archive bodyS)
@@ -91,10 +91,10 @@
        .let [@loop (_.var (///reference.artifact [artifact_module artifact_id]))
              locals (|> initsO+
                         list.enumeration
-                        (list#each (|>> product.left (n.+ start) //case.register)))
+                        (list#each (|>> product.left (n.+ start) //when.register)))
              [declaration instantiation] (is [Statement Expression]
-                                             (case (|> (synthesis.path/then bodyS)
-                                                       //case.dependencies
+                                             (when (|> (synthesis.path/then bodyS)
+                                                       //when.dependencies
                                                        (set.of_list _.hash)
                                                        (set.difference (set.of_list _.hash locals))
                                                        set.list)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/runtime.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/runtime.lux
index e8ba62726..b365b536e 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/runtime.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/runtime.lux
@@ -129,7 +129,7 @@
       (macro.with_symbols [g!_]
         (let [runtime (code.local (///reference.artifact [..module_id runtime_id]))
               runtime_name (` (_.var (, (code.text (%.code runtime)))))]
-          (case declaration
+          (when declaration
             {.#Left name}
             (macro.with_symbols [g!_]
               (let [g!name (code.local name)]
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/structure.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/structure.lux
index e3b0c8c66..c623bd592 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/structure.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/structure.lux
@@ -18,7 +18,7 @@
 
 (def .public (tuple phase archive elemsS+)
   (Generator (Tuple Synthesis))
-  (case elemsS+
+  (when elemsS+
     {.#End}
     (///////phase#in (//primitive.text /////synthesis.unit))
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/case.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/when.lux
index 5924848e8..7e9e383ca 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/case.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/lua/when.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except case exec let if)
+  [lux (.except when exec let if)
    [abstract
     ["[0]" monad (.only do)]]
    [data
@@ -22,7 +22,7 @@
    ["[1][0]" reference]
    ["/[1]" //
     ["[1][0]" synthesis
-     ["[1]/[0]" case]]
+     ["[1]/[0]" when]]
     ["/[1]" //
      ["[1][0]" synthesis (.only Synthesis Path)
       [access
@@ -160,7 +160,7 @@
                                                   (|> idx .int _.int)))
           (.if simple?
             (_.when (_.= _.nil @temp)
-                    fail!)
+              fail!)
             (_.if (_.= _.nil @temp)
               fail!
               (..push! @temp)))))]
@@ -183,7 +183,7 @@
 (def (pattern_matching' statement expression archive)
   (-> Phase! Phase Archive Path (Operation Statement))
   (function (again pathP)
-    (.case pathP
+    (.when pathP
       {/////synthesis.#Then bodyS}
       (statement expression archive bodyS)
 
@@ -196,7 +196,7 @@
       {/////synthesis.#Bit_Fork when thenP elseP}
       (do [! ///////phase.monad]
         [then! (again thenP)
-         else! (.case elseP
+         else! (.when elseP
                  {.#Some elseP}
                  (again elseP)
 
@@ -269,22 +269,22 @@
     (in (all _.then
              (_.while (_.boolean true)
                       pattern_matching!)
-             (_.statement (|> (_.var "error") (_.apply (list (_.string ////synthesis/case.pattern_matching_error)))))))))
+             (_.statement (|> (_.var "error") (_.apply (list (_.string ////synthesis/when.pattern_matching_error)))))))))
 
 (def .public dependencies
   (-> Path (List Var))
-  (|>> ////synthesis/case.storage
-       (the ////synthesis/case.#dependencies)
+  (|>> ////synthesis/when.storage
+       (the ////synthesis/when.#dependencies)
        set.list
        (list#each (function (_ variable)
-                    (.case variable
+                    (.when variable
                       {///////variable.#Local register}
                       (..register register)
                       
                       {///////variable.#Foreign register}
                       (..capture register))))))
 
-(def .public (case! statement expression archive [valueS pathP])
+(def .public (when! statement expression archive [valueS pathP])
   (Generator! [Synthesis Path])
   (do ///////phase.monad
     [stack_init (expression archive valueS)
@@ -295,10 +295,10 @@
              (_.local/1 @savepoint (_.array (list)))
              pattern_matching!))))
 
-(def .public (case statement expression archive [valueS pathP])
+(def .public (when statement expression archive [valueS pathP])
   (-> Phase! (Generator [Synthesis Path]))
   (|> [valueS pathP]
-      (..case! statement expression archive)
+      (..when! statement expression archive)
       (at ///////phase.monad each
           (|>> (_.closure (list))
                (_.apply (list))))))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php.lux
index 293366280..12e2dffd3 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php.lux
@@ -15,7 +15,7 @@
   ["[1][0]" primitive]
   ["[1][0]" structure]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" loop]
   ["[1][0]" function]
   ["/[1]" //
@@ -32,7 +32,7 @@
 
 (def (statement expression archive synthesis)
   Phase!
-  (case synthesis
+  (when synthesis
     (^.with_template [<tag>]
       [(<tag> value)
        (//////phase#each _.return (expression archive synthesis))])
@@ -51,14 +51,14 @@
     ([////synthesis.#Reference]
      [////synthesis.#Extension])
 
-    (////synthesis.branch/case case)
-    (/case.case! statement expression archive case)
+    (////synthesis.branch/when when)
+    (/when.when! statement expression archive when)
 
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (<generator> statement expression archive value)])
-    ([////synthesis.branch/let /case.let!]
-     [////synthesis.branch/if /case.if!]
+    ([////synthesis.branch/let /when.let!]
+     [////synthesis.branch/if /when.if!]
      [////synthesis.loop/scope /loop.scope!]
      [////synthesis.loop/again /loop.again!])
 
@@ -70,7 +70,7 @@
 
 (def .public (expression archive synthesis)
   Phase
-  (case synthesis
+  (when synthesis
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (//////phase#in (<generator> value))])
@@ -87,15 +87,15 @@
        (<generator> expression archive value)])
     ([////synthesis.variant /structure.variant]
      [////synthesis.tuple /structure.tuple]
-     [////synthesis.branch/let /case.let]
-     [////synthesis.branch/if /case.if]
-     [////synthesis.branch/get /case.get]
+     [////synthesis.branch/let /when.let]
+     [////synthesis.branch/if /when.if]
+     [////synthesis.branch/get /when.get]
      [////synthesis.function/apply /function.apply])
 
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (<generator> statement expression archive value)])
-    ([////synthesis.branch/case /case.case]
+    ([////synthesis.branch/when /when.when]
      [////synthesis.loop/scope /loop.scope]
      [////synthesis.function/abstraction /function.function])
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/function.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/function.lux
index b2ca21671..e4195f3d4 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/function.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/function.lux
@@ -17,7 +17,7 @@
  ["[0]" //
   ["[1][0]" runtime (.only Operation Phase Phase! Generator)]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["//[1]" ///
@@ -42,7 +42,7 @@
   (|>> (///reference.foreign //reference.system) as_expected))
 
 (def input
-  (|>> ++ //case.register))
+  (|>> ++ //when.register))
 
 (def (@scope function_name)
   (-> Context Label)
@@ -50,7 +50,7 @@
 
 (def (with_closure inits @selfG @selfL body!)
   (-> (List Expression) Global Var Statement [Statement Expression])
-  (case inits
+  (when inits
     {.#End}
     [(all _.then
           (_.set! @selfL (_.closure (list (_.reference @selfL)) (list) body!))
@@ -84,7 +84,7 @@
            @scope (..@scope function_name)
            @selfG (_.global (///reference.artifact function_name))
            @selfL (_.var (///reference.artifact function_name))
-           initialize_self! (_.set! (//case.register 0) @selfL)
+           initialize_self! (_.set! (//when.register 0) @selfL)
            initialize! (list#mix (.function (_ post pre!)
                                    (all _.then
                                         pre!
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/loop.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/loop.lux
index 5c3682738..b4c3804e8 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/loop.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/loop.lux
@@ -18,12 +18,12 @@
      ["_" php (.only Var Expression Label Statement)]]]]]
  ["[0]" //
   [runtime (.only Operation Phase Phase! Generator Generator!)]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["/[1]" //
     [synthesis
-     ["[0]" case]]
+     ["[0]" when]]
     ["/[1]" //
      ["[0]" synthesis (.only Scope Synthesis)]
      ["[1][0]" generation]
@@ -44,14 +44,14 @@
   (|> bindings
       list.enumeration
       (list#each (function (_ [register value])
-                   (let [variable (//case.register (n.+ offset register))]
+                   (let [variable (//when.register (n.+ offset register))]
                      (_.set! variable value))))
       list.reversed
       (list#mix _.then body)))
 
 (def .public (scope! statement expression archive [start initsS+ bodyS])
   (Generator! (Scope Synthesis))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (statement expression archive bodyS)
@@ -70,7 +70,7 @@
 
 (def .public (scope statement expression archive [start initsS+ bodyS])
   (-> Phase! (Generator (Scope Synthesis)))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (expression archive bodyS)
@@ -82,15 +82,15 @@
                                               (..scope! statement expression archive [start initsS+ bodyS]))
        .let [locals (|> initsS+
                         list.enumeration
-                        (list#each (|>> product.left (n.+ start) //case.register _.parameter)))
+                        (list#each (|>> product.left (n.+ start) //when.register _.parameter)))
              @loop (_.constant (///reference.artifact [loop_module loop_artifact]))
              loop_variables (set.of_list _.hash (list#each product.right locals))
              referenced_variables (is (-> Synthesis (Set Var))
                                       (|>> synthesis.path/then
-                                           //case.dependencies
+                                           //when.dependencies
                                            (set.of_list _.hash)))
              [declaration instantiation] (is [Statement Expression]
-                                             (case (|> (list#each referenced_variables initsS+)
+                                             (when (|> (list#each referenced_variables initsS+)
                                                        (list#mix set.union (referenced_variables bodyS))
                                                        (set.difference loop_variables)
                                                        set.list)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/runtime.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/runtime.lux
index bff0a6cf0..b1d1abe87 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/runtime.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/runtime.lux
@@ -96,7 +96,7 @@
       (macro.with_symbols [g!_]
         (let [runtime (code.local (///reference.artifact [..module_id runtime_id]))
               runtime_name (` (_.constant (, (code.text (%.code runtime)))))]
-          (case declaration
+          (when declaration
             {.#Left name}
             (macro.with_symbols [g!_]
               (let [g!name (code.local name)]
@@ -606,7 +606,7 @@
         i64_error (_.string (format "Cannot run program!" text.new_line
                                     "Lux/PHP programs require 64-bit PHP builds!"))]
     (_.when (_.not i64_support?)
-            (_.throw (_.new (_.constant "Exception") (list i64_error))))))
+      (_.throw (_.new (_.constant "Exception") (list i64_error))))))
 
 (def runtime
   Statement
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/structure.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/structure.lux
index 749ba0f5d..239d34609 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/structure.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/structure.lux
@@ -19,7 +19,7 @@
 
 (def .public (tuple expression archive elemsS+)
   (Generator (Tuple Synthesis))
-  (case elemsS+
+  (when elemsS+
     {.#End}
     (///////phase#in (//primitive.text /////synthesis.unit))
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/case.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/when.lux
index 816b77d0f..fc703eb8b 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/case.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/php/when.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except case let if)
+  [lux (.except when let if)
    [abstract
     ["[0]" monad (.only do)]]
    [data
@@ -26,7 +26,7 @@
    ["[1][0]" reference]
    ["/[1]" //
     ["[1][0]" synthesis
-     ["[1]/[0]" case]]
+     ["[1]/[0]" when]]
     ["/[1]" //
      ["[1][0]" synthesis (.only Member Synthesis Path)]
      ["[1][0]" generation]
@@ -87,7 +87,7 @@
   (do ///////phase.monad
     [valueG (expression archive valueS)]
     (in (list#mix (function (_ side source)
-                    (.let [method (.case side
+                    (.let [method (.when side
                                     (^.with_template [<side> <accessor>]
                                       [(<side> lefts)
                                        (<accessor> (_.int (.int lefts)))])
@@ -142,7 +142,7 @@
           (_.set! @temp (|> idx <prep> .int _.int (//runtime.sum//get ..peek <flag>)))
           (.if simple?
             (_.when (_.is_null/1 @temp)
-                    fail!)
+              fail!)
             (_.if (_.is_null/1 @temp)
               fail!
               (..push! @temp)))))]
@@ -165,7 +165,7 @@
 (def (pattern_matching' statement expression archive)
   (Generator! Path)
   (function (again pathP)
-    (.case pathP
+    (.when pathP
       {/////synthesis.#Then bodyS}
       (statement expression archive bodyS)
 
@@ -178,7 +178,7 @@
       {/////synthesis.#Bit_Fork when thenP elseP}
       (do [! ///////phase.monad]
         [then! (again thenP)
-         else! (.case elseP
+         else! (.when elseP
                  {.#Some elseP}
                  (again elseP)
 
@@ -235,7 +235,7 @@
                               then!)))
 
       ... (/////synthesis.!multi_pop nextP)
-      ... (.let [[extra_pops nextP'] (////synthesis/case.count_pops nextP)]
+      ... (.let [[extra_pops nextP'] (////synthesis/when.count_pops nextP)]
       ...   (do ///////phase.monad
       ...     [next! (again nextP')]
       ...     (///////phase#in (all _.then
@@ -258,22 +258,22 @@
     (in (all _.then
              (_.do_while (_.bool false)
                          iteration!)
-             (_.throw (_.new (_.constant "Exception") (list (_.string ////synthesis/case.pattern_matching_error))))))))
+             (_.throw (_.new (_.constant "Exception") (list (_.string ////synthesis/when.pattern_matching_error))))))))
 
 (def .public dependencies
   (-> Path (List Var))
-  (|>> ////synthesis/case.storage
-       (the ////synthesis/case.#dependencies)
+  (|>> ////synthesis/when.storage
+       (the ////synthesis/when.#dependencies)
        set.list
        (list#each (function (_ variable)
-                    (.case variable
+                    (.when variable
                       {///////variable.#Local register}
                       (..register register)
                       
                       {///////variable.#Foreign register}
                       (..capture register))))))
 
-(def .public (case! statement expression archive [valueS pathP])
+(def .public (when! statement expression archive [valueS pathP])
   (Generator! [Synthesis Path])
   (do ///////phase.monad
     [stack_init (expression archive valueS)
@@ -283,15 +283,15 @@
              (_.set! @savepoint (_.array/* (list)))
              pattern_matching!))))
 
-(def .public (case statement expression archive [valueS pathP])
+(def .public (when statement expression archive [valueS pathP])
   (-> Phase! (Generator [Synthesis Path]))
   (do [! ///////phase.monad]
-    [[[case_module case_artifact] case!] (/////generation.with_new_context archive
-                                           (case! statement expression archive [valueS pathP]))
-     .let [@case (_.constant (///reference.artifact [case_module case_artifact]))
+    [[[when_module when_artifact] when!] (/////generation.with_new_context archive
+                                           (when! statement expression archive [valueS pathP]))
+     .let [@when (_.constant (///reference.artifact [when_module when_artifact]))
            @dependencies+ (..dependencies (/////synthesis.path/seq (/////synthesis.path/then valueS)
                                                                    pathP))
-           declaration (_.define_function @case (list#each _.parameter @dependencies+) case!)]
+           declaration (_.define_function @when (list#each _.parameter @dependencies+) when!)]
      _ (/////generation.execute! declaration)
-     _ (/////generation.save! case_artifact declaration)]
-    (in (_.apply @dependencies+ @case))))
+     _ (/////generation.save! when_artifact declaration)]
+    (in (_.apply @dependencies+ @when))))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python.lux
index cd48b763b..b2692261f 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python.lux
@@ -16,7 +16,7 @@
   ["[1][0]" structure]
   ["[1][0]" reference]
   ["[1][0]" function]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" loop]
   ["/[1]" //
    ["[1][0]" reference]
@@ -37,7 +37,7 @@
 
 (def .public (expression archive synthesis)
   Phase
-  (case synthesis
+  (when synthesis
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (//////phase#in (<generator> value))])
@@ -52,17 +52,17 @@
     ([////synthesis.variant /structure.variant]
      [////synthesis.tuple /structure.tuple]
      
-     [////synthesis.branch/exec /case.exec]
-     [////synthesis.branch/let /case.let]
-     [////synthesis.branch/if /case.if]
-     [////synthesis.branch/get /case.get]
+     [////synthesis.branch/exec /when.exec]
+     [////synthesis.branch/let /when.let]
+     [////synthesis.branch/if /when.if]
+     [////synthesis.branch/get /when.get]
      
      [////synthesis.function/apply /function.apply])
 
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (<generator> ///extension/common.statement expression archive value)])
-    ([////synthesis.branch/case /case.case]
+    ([////synthesis.branch/when /when.when]
      [////synthesis.loop/scope /loop.scope]
      [////synthesis.function/abstraction /function.function])
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/function.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/function.lux
index 1d1021d11..7afc45ccb 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/function.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/function.lux
@@ -15,7 +15,7 @@
  ["[0]" //
   [runtime (.only Operation Phase Generator Phase! Generator!)]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" loop]
   ["/[1]" //
    ["[1][0]" reference]
@@ -48,7 +48,7 @@
 
 (def (with_closure function_id @function inits function_definition)
   (-> artifact.ID SVar (List (Expression Any)) (Statement Any) (Operation (Expression Any)))
-  (case inits
+  (when inits
     {.#End}
     (do ///////phase.monad
       [_ (/////generation.execute! function_definition)
@@ -68,7 +68,7 @@
       (in (_.apply inits @function)))))
 
 (def input
-  (|>> ++ //case.register))
+  (|>> ++ //when.register))
 
 (def .public (function statement expression archive [environment arity bodyS])
   (-> Phase! (Generator (Abstraction Synthesis)))
@@ -84,7 +84,7 @@
            @self (_.var (///reference.artifact [function_module function_artifact]))
            apply_poly (.function (_ args func)
                         (_.apply (list (_.splat_poly args)) func))
-           initialize_self! (_.set (list (//case.register 0)) @self)
+           initialize_self! (_.set (list (//when.register 0)) @self)
            initialize! (list#mix (.function (_ post pre!)
                                    (all _.then
                                         pre!
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/loop.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/loop.lux
index d767eeeeb..16df5397a 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/loop.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/loop.lux
@@ -18,12 +18,12 @@
      ["_" python (.only Expression SVar Statement)]]]]]
  ["[0]" //
   [runtime (.only Operation Phase Generator Phase! Generator!)]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["/[1]" //
     [synthesis
-     ["[0]" case]]
+     ["[0]" when]]
     ["/[1]" //
      ["[0]" synthesis (.only Scope Synthesis)]
      ["[1][0]" generation]
@@ -40,7 +40,7 @@
   (-> Register (List (Expression Any)) (Statement Any) (Statement Any))
   (let [variables (|> bindings
                       list.enumeration
-                      (list#each (|>> product.left (n.+ offset) //case.register)))]
+                      (list#each (|>> product.left (n.+ offset) //when.register)))]
     (all _.then
          (_.set variables (_.multi bindings))
          body)))
@@ -53,7 +53,7 @@
 
 (def .public (scope! statement expression archive [start initsS+ bodyS])
   (Generator! (Scope Synthesis))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (statement expression archive bodyS)
@@ -70,7 +70,7 @@
 
 (def .public (scope statement expression archive [start initsS+ bodyS])
   (-> Phase! (Generator (Scope Synthesis)))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (expression archive bodyS)
@@ -86,13 +86,13 @@
        .let [@loop (_.var (///reference.artifact [loop_module loop_artifact]))
              locals (|> initsS+
                         list.enumeration
-                        (list#each (|>> product.left (n.+ start) //case.register)))
+                        (list#each (|>> product.left (n.+ start) //when.register)))
              actual_loop (<| (_.def @loop locals)
                              ..set_scope
                              body!)
              [declaration instantiation] (is [(Statement Any) (Expression Any)]
-                                             (case (|> (synthesis.path/then bodyS)
-                                                       //case.dependencies
+                                             (when (|> (synthesis.path/then bodyS)
+                                                       //when.dependencies
                                                        (set.of_list _.hash)
                                                        (set.difference (set.of_list _.hash locals))
                                                        set.list)
@@ -115,7 +115,7 @@
   (Generator! (List Synthesis))
   (do [! ///////phase.monad]
     [offset /////generation.anchor
-     @temp (//case.symbol "lux_again_values")
+     @temp (//when.symbol "lux_again_values")
      argsO+ (monad.each ! (expression archive) argsS+)
      .let [re_binds (|> argsO+
                         list.enumeration
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/runtime.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/runtime.lux
index d045b7d8e..38c5d87e3 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/runtime.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/runtime.lux
@@ -127,7 +127,7 @@
                                  (<code>.form (<>.and <code>.local
                                                       (<>.some <code>.local))))
               code <code>.any])
-    (case declaration
+    (when declaration
       {.#Left name}
       (macro.with_symbols [g!_]
         (let [nameC (code.local name)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/structure.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/structure.lux
index 428320d23..f89cf244b 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/structure.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/structure.lux
@@ -18,7 +18,7 @@
 
 (def .public (tuple generate archive elemsS+)
   (Generator (Tuple Synthesis))
-  (case elemsS+
+  (when elemsS+
     {.#End}
     (///////phase#in (//primitive.text /////synthesis.unit))
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/case.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/when.lux
index 090c2587e..3666dc9fc 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/case.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/python/when.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except case exec let if symbol)
+  [lux (.except when exec let if symbol)
    [abstract
     ["[0]" monad (.only do)]]
    [data
@@ -26,7 +26,7 @@
    ["[1][0]" reference]
    ["/[1]" //
     [synthesis
-     ["[0]" case]]
+     ["[0]" when]]
     ["/[1]" //
      ["[1][0]" generation]
      ["[1][0]" synthesis (.only Synthesis Path)
@@ -164,7 +164,7 @@
                                                   (|> idx .int _.int)))
           (.if simple?
             (_.when (_.= _.none @temp)
-                    fail_pm!)
+              fail_pm!)
             (_.if (_.= _.none @temp)
               fail_pm!
               (..push! @temp))
@@ -201,11 +201,11 @@
 (def (primitive_pattern_matching again pathP)
   (-> (-> Path (Operation (Statement Any)))
       (-> Path (Operation (Maybe (Statement Any)))))
-  (.case pathP
+  (.when pathP
     {/////synthesis.#Bit_Fork when thenP elseP}
     (do [! ///////phase.monad]
       [then! (again thenP)
-       else! (.case elseP
+       else! (.when elseP
                {.#Some elseP}
                (again elseP)
 
@@ -244,12 +244,12 @@
   (function (again pathP)
     (do [! ///////phase.monad]
       [?output (primitive_pattern_matching again pathP)]
-      (.case ?output
+      (.when ?output
         {.#Some output}
         (in output)
 
         {.#None}
-        (.case pathP
+        (.when pathP
           {/////synthesis.#Then bodyS}
           (statement expression archive bodyS)
 
@@ -287,7 +287,7 @@
                                   then!)))
 
           (/////synthesis.!multi_pop nextP)
-          (.let [[extra_pops nextP'] (case.count_pops nextP)]
+          (.let [[extra_pops nextP'] (when.count_pops nextP)]
             (do !
               [next! (again nextP')]
               (///////phase#in (all _.then
@@ -318,22 +318,22 @@
     (in (all _.then
              (..with_looping in_closure? g!once
                pattern_matching!)
-             (_.raise (_.Exception/1 (_.string case.pattern_matching_error)))))))
+             (_.raise (_.Exception/1 (_.string when.pattern_matching_error)))))))
 
 (def .public dependencies
   (-> Path (List SVar))
-  (|>> case.storage
-       (the case.#dependencies)
+  (|>> when.storage
+       (the when.#dependencies)
        set.list
        (list#each (function (_ variable)
-                    (.case variable
+                    (.when variable
                       {///////variable.#Local register}
                       (..register register)
                       
                       {///////variable.#Foreign register}
                       (..capture register))))))
 
-(def .public (case! in_closure? statement expression archive [valueS pathP])
+(def .public (when! in_closure? statement expression archive [valueS pathP])
   (-> Bit (Generator! [Synthesis Path]))
   (do ///////phase.monad
     [stack_init (expression archive valueS)
@@ -344,19 +344,19 @@
              pattern_matching!
              ))))
 
-(def .public (case statement expression archive [valueS pathP])
+(def .public (when statement expression archive [valueS pathP])
   (-> Phase! (Generator [Synthesis Path]))
   (do ///////phase.monad
     [dependencies (cache.path_dependencies archive pathP)
-     [[case_module case_artifact] pattern_matching!] (/////generation.with_new_context
+     [[when_module when_artifact] pattern_matching!] (/////generation.with_new_context
                                                        archive
                                                        dependencies
-                                                       (case! true statement expression archive [valueS pathP]))
-     .let [@case (_.var (///reference.artifact [case_module case_artifact]))
+                                                       (when! true statement expression archive [valueS pathP]))
+     .let [@when (_.var (///reference.artifact [when_module when_artifact]))
            @dependencies+ (..dependencies (/////synthesis.path/seq (/////synthesis.path/then valueS)
                                                                    pathP))
-           declaration (_.def @case @dependencies+
+           declaration (_.def @when @dependencies+
                          pattern_matching!)]
      _ (/////generation.execute! declaration)
-     _ (/////generation.save! case_artifact {.#None} declaration)]
-    (in (_.apply @dependencies+ @case))))
+     _ (/////generation.save! when_artifact {.#None} declaration)]
+    (in (_.apply @dependencies+ @when))))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r.lux
index 7741ccce0..cf20229d8 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r.lux
@@ -13,7 +13,7 @@
   ["[1][0]" primitive]
   ["[1][0]" structure]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" loop]
   ["[1][0]" function]
   ["/[1]" //
@@ -30,7 +30,7 @@
 
 (def .public (generate archive synthesis)
   Phase
-  (case synthesis
+  (when synthesis
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (//////phase#in (<generator> value))])
@@ -47,12 +47,12 @@
        (<generator> generate archive value)])
     ([////synthesis.variant /structure.variant]
      [////synthesis.tuple /structure.tuple]
-     [////synthesis.branch/let /case.let]
-     [////synthesis.branch/if /case.if]
-     [////synthesis.branch/get /case.get]
+     [////synthesis.branch/let /when.let]
+     [////synthesis.branch/if /when.if]
+     [////synthesis.branch/get /when.get]
      [////synthesis.function/apply /function.apply]
 
-     [////synthesis.branch/case /case.case]
+     [////synthesis.branch/when /when.when]
      [////synthesis.loop/scope /loop.scope]
      [////synthesis.loop/again /loop.again]
      [////synthesis.function/abstraction /function.function])
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/function.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/function.lux
index 80f8ac48c..bf6d09b19 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/function.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/function.lux
@@ -17,7 +17,7 @@
  ["[0]" //
   ["[1][0]" runtime (.only Operation Phase Generator)]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["//[1]" ///
@@ -42,7 +42,7 @@
 
 (def (with_closure function_id $function inits function_definition)
   (-> artifact.ID SVar (List Expression) Expression (Operation Expression))
-  (case inits
+  (when inits
     {.#End}
     (do ///////phase.monad
       [_ (/////generation.execute! function_definition)
@@ -56,7 +56,7 @@
                                         (_.function (|> inits
                                                         list.size
                                                         list.indices
-                                                        (list#each //case.capture))
+                                                        (list#each //when.capture))
                                           (all _.then
                                                function_definition
                                                $function)))]
@@ -69,7 +69,7 @@
 
 (def (input_declaration register)
   (-> Register Expression)
-  (_.set! (|> register ++ //case.register)
+  (_.set! (|> register ++ //when.register)
           (|> $curried (_.item (|> register ++ .int _.int)))))
 
 (def .public (function expression archive [environment arity bodyS])
@@ -94,7 +94,7 @@
                            (_.set! $num_args (_.length $curried))
                            (_.cond (list [(|> $num_args (_.= arityO))
                                           (all _.then
-                                               (_.set! (//case.register 0) $self)
+                                               (_.set! (//when.register 0) $self)
                                                (|> arity
                                                    list.indices
                                                    (list#each input_declaration)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/loop.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/loop.lux
index 35477e3f7..7a72081e9 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/loop.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/loop.lux
@@ -18,12 +18,12 @@
      ["_" r]]]]]
  ["[0]" //
   [runtime (.only Operation Phase Generator)]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["/[1]" //
     [synthesis
-     ["[0]" case]]
+     ["[0]" when]]
     ["/[1]" //
      ["[0]" synthesis (.only Scope Synthesis)]
      ["[1][0]" generation]
@@ -36,7 +36,7 @@
 
 (def .public (scope expression archive [offset initsS+ bodyS])
   (Generator (Scope Synthesis))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (expression archive bodyS)
@@ -54,7 +54,7 @@
                         (_.function (|> initsS+
                                         list.size
                                         list.indices
-                                        (list#each (|>> (n.+ offset) //case.register)))
+                                        (list#each (|>> (n.+ offset) //when.register)))
                           bodyO))
                 (_.apply initsO+ $scope)))))))
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/procedure/common.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/procedure/common.lux
index a64f95bc9..f57141564 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/procedure/common.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/procedure/common.lux
@@ -20,7 +20,7 @@
              (host [r (.only Expression)])))
  [///]
  (/// ["[0]T" runtime]
-      ["[0]T" case]
+      ["[0]T" when]
       ["[0]T" function]
       ["[0]T" loop]))
 
@@ -56,7 +56,7 @@
 
 (def (lux//if [testO thenO elseO])
   Trinary
-  (caseT.translate_if testO thenO elseO))
+  (whenT.translate_if testO thenO elseO))
 
 (def (lux//try riskyO)
   Unary
@@ -74,7 +74,7 @@
   (-> Text Proc)
   (function (_ proc_name)
     (function (_ translate inputsS)
-      (case (s.result inputsS (all p.and s.nat (s.tuple (p.many s.any)) s.any))
+      (when (s.result inputsS (all p.and s.nat (s.tuple (p.many s.any)) s.any))
         {e.#Success [offset initsS+ bodyS]}
         (loopT.translate_loop translate offset initsS+ bodyS)
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/procedure/host.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/procedure/host.lux
index b5a3fcb3a..1b588bc61 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/procedure/host.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/procedure/host.lux
@@ -24,7 +24,7 @@
 
 ... (def (lua//global proc translate inputs)
 ...   (-> Text @.Proc)
-...   (case inputs
+...   (when inputs
 ...     (list [_ {.#Text name}])
 ...     (do macro.Monad<Meta>
 ...       []
@@ -35,7 +35,7 @@
 
 ... (def (lua//call proc translate inputs)
 ...   (-> Text @.Proc)
-...   (case inputs
+...   (when inputs
 ...     (list.partial functionS argsS+)
 ...     (do [@ macro.Monad<Meta>]
 ...       [functionO (translate functionS)
@@ -55,7 +55,7 @@
 
 ... (def (table//call proc translate inputs)
 ...   (-> Text @.Proc)
-...   (case inputs
+...   (when inputs
 ...     (list.partial tableS [_ {.#Text field}] argsS+)
 ...     (do [@ macro.Monad<Meta>]
 ...       [tableO (translate tableS)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/runtime.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/runtime.lux
index c23b725d5..261cba579 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/runtime.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/runtime.lux
@@ -99,7 +99,7 @@
       (macro.with_symbols [g!_]
         (let [runtime (code.local (///reference.artifact [..module_id runtime_id]))
               runtime_name (` (_.var (, (code.text (%.code runtime)))))]
-          (case declaration
+          (when declaration
             {.#Left name}
             (let [g!name (code.local name)]
               (in (list (` (def .public (, g!name)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/structure.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/structure.lux
index b381f8d63..77b7a3f62 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/structure.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/structure.lux
@@ -20,7 +20,7 @@
 
 (def .public (tuple expression archive elemsS+)
   (Generator (Tuple Synthesis))
-  (case elemsS+
+  (when elemsS+
     {.#End}
     (///////phase#in (//primitive.text /////synthesis.unit))
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/case.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/when.lux
index cc47ed212..0f2a0954c 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/case.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/r/when.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except case let if)
+  [lux (.except when let if)
    [abstract
     ["[0]" monad (.only do)]]
    [data
@@ -27,7 +27,7 @@
    ["[1][0]" reference]
    ["/[1]" //
     ["[1][0]" synthesis
-     ["[1]/[0]" case]]
+     ["[1]/[0]" when]]
     ["/[1]" //
      ["[1][0]" synthesis (.only Member Synthesis Path)]
      ["[1][0]" generation]
@@ -69,7 +69,7 @@
   (do ///////phase.monad
     [valueO (expression archive valueS)]
     (in (list#mix (function (_ side source)
-                    (.let [method (.case side
+                    (.let [method (.when side
                                     (^.with_template [<side> <accessor>]
                                       [(<side> lefts)
                                        (<accessor> (_.int (.int lefts)))])
@@ -136,7 +136,7 @@
 (def (pattern_matching' expression archive)
   (Generator Path)
   (function (again pathP)
-    (.case pathP
+    (.when pathP
       {/////synthesis.#Then bodyS}
       (expression archive bodyS)
 
@@ -149,7 +149,7 @@
       {/////synthesis.#Bit_Fork when thenP elseP}
       (do [! ///////phase.monad]
         [then! (again thenP)
-         else! (.case elseP
+         else! (.when elseP
                  {.#Some elseP}
                  (again elseP)
 
@@ -231,7 +231,7 @@
                {.#Some (..catch (_.stop (_.string "Invalid expression for pattern-matching.")))}
                {.#None}))))
 
-(def .public (case expression archive [valueS pathP])
+(def .public (when expression archive [valueS pathP])
   (Generator [Synthesis Path])
   (do [! ///////phase.monad]
     [valueO (expression archive valueS)]
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/reference.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/reference.lux
index ef720c4ae..2ec80b679 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/reference.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/reference.lux
@@ -83,7 +83,7 @@
 (def .public (variable system variable)
   (All (_ expression)
     (-> (System expression) Variable expression))
-  (case variable
+  (when variable
     {variable.#Local register}
     (..local system register)
     
@@ -93,7 +93,7 @@
 (def .public (reference system archive reference)
   (All (_ anchor expression declaration)
     (-> (System expression) Archive Reference (////generation.Operation anchor expression declaration expression)))
-  (case reference
+  (when reference
     {reference.#Constant value}
     (..constant system archive value)
     
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby.lux
index f3e5aed3c..9c2719467 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby.lux
@@ -16,7 +16,7 @@
   ["[1][0]" structure]
   ["[1][0]" reference]
   ["[1][0]" function]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" loop]
   ["/[1]" //
    ["[1][0]" reference]
@@ -37,7 +37,7 @@
 
 (def (expression archive synthesis)
   Phase
-  (case synthesis
+  (when synthesis
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (//////phase#in (<generator> value))])
@@ -52,17 +52,17 @@
     ([////synthesis.variant /structure.variant]
      [////synthesis.tuple /structure.tuple]
      
-     [////synthesis.branch/exec /case.exec]
-     [////synthesis.branch/let /case.let]
-     [////synthesis.branch/if /case.if]
-     [////synthesis.branch/get /case.get]
+     [////synthesis.branch/exec /when.exec]
+     [////synthesis.branch/let /when.let]
+     [////synthesis.branch/if /when.if]
+     [////synthesis.branch/get /when.get]
      
      [////synthesis.function/apply /function.apply])
 
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (<generator> ///extension/common.statement expression archive value)])
-    ([////synthesis.branch/case /case.case]
+    ([////synthesis.branch/when /when.when]
      [////synthesis.loop/scope /loop.scope]
      [////synthesis.function/abstraction /function.function])
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/function.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/function.lux
index 51cf79c55..fc63bb4fa 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/function.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/function.lux
@@ -15,7 +15,7 @@
  ["[0]" //
   [runtime (.only Operation Phase Generator Phase! Generator!)]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" loop]
   ["/[1]" //
    ["[1][0]" reference]
@@ -47,7 +47,7 @@
 (def (with_closure inits self function_definition)
   (-> (List Expression) Text Expression [Statement Expression])
   (let [@self (_.global self)]
-    (case inits
+    (when inits
       {.#End}
       [(_.set (list @self) function_definition)
        @self]
@@ -63,7 +63,7 @@
        (_.apply_lambda inits @self)])))
 
 (def input
-  (|>> ++ //case.register))
+  (|>> ++ //when.register))
 
 (def .public (function statement expression archive [environment arity bodyS])
   (-> Phase! (Generator (Abstraction Synthesis)))
@@ -79,13 +79,13 @@
            limitO (|> arity -- .int _.int)
            @num_args (_.local "num_args")
            @self (is _.Location
-                     (case closureO+
+                     (when closureO+
                        {.#End}
                        (_.global function_name)
 
                        _
                        (_.local function_name)))
-           initialize_self! (_.set (list (//case.register 0)) @self)
+           initialize_self! (_.set (list (//when.register 0)) @self)
            initialize! (list#mix (.function (_ post pre!)
                                    (all _.then
                                         pre!
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/loop.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/loop.lux
index 1a82b9e18..25feac999 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/loop.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/loop.lux
@@ -18,12 +18,12 @@
      ["_" ruby (.only Expression LVar Statement)]]]]]
  ["[0]" //
   [runtime (.only Operation Phase Generator Phase! Generator!)]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["/[1]" //
     [synthesis
-     ["[0]" case]]
+     ["[0]" when]]
     ["/[1]" //
      ["[0]" synthesis (.only Scope Synthesis)]
      ["[1][0]" generation]
@@ -36,7 +36,7 @@
   (-> Register (List Expression) Statement Statement)
   (let [variables (|> bindings
                       list.enumeration
-                      (list#each (|>> product.left (n.+ offset) //case.register)))]
+                      (list#each (|>> product.left (n.+ offset) //when.register)))]
     (all _.then
          (_.set variables (_.multi bindings))
          body)))
@@ -50,7 +50,7 @@
 
 (def .public (scope! statement expression archive [start initsS+ bodyS])
   (Generator! (Scope Synthesis))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (statement expression archive bodyS)
@@ -67,7 +67,7 @@
 
 (def .public (scope statement expression archive [start initsS+ bodyS])
   (-> Phase! (Generator (Scope Synthesis)))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (expression archive bodyS)
@@ -84,7 +84,7 @@
   (Generator! (List Synthesis))
   (do [! ///////phase.monad]
     [offset /////generation.anchor
-     @temp (//case.symbol "lux_again_values")
+     @temp (//when.symbol "lux_again_values")
      argsO+ (monad.each ! (expression archive) argsS+)
      .let [re_binds (|> argsO+
                         list.enumeration
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/runtime.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/runtime.lux
index b193b5b84..9cb620e31 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/runtime.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/runtime.lux
@@ -112,7 +112,7 @@
     (do meta.monad
       [runtime_id meta.seed]
       (macro.with_symbols [g!_]
-        (case declaration
+        (when declaration
           {.#Left name}
           (macro.with_symbols [g!_]
             (let [runtime (code.local (///reference.artifact [..module_id runtime_id]))
@@ -599,13 +599,13 @@
   Statement
   (all _.then
        (_.when ..mruby?
-               ... We're in mRuby/DragonRuby territory.
-               (_.statement
-                (_.do "class_eval" (list) {.#Some [(list (_.local "_"))
-                                                   (_.statement
-                                                    (_.alias_method/2 (_.string "remainder")
-                                                                      (_.string "remainder_of_divide")))]}
-                  $Numeric)))
+         ... We're in mRuby/DragonRuby territory.
+         (_.statement
+          (_.do "class_eval" (list) {.#Some [(list (_.local "_"))
+                                             (_.statement
+                                              (_.alias_method/2 (_.string "remainder")
+                                                                (_.string "remainder_of_divide")))]}
+            $Numeric)))
        runtime//adt
        runtime//lux
        runtime//i64
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/structure.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/structure.lux
index 5947bc8c4..a879af9d3 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/structure.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/structure.lux
@@ -18,7 +18,7 @@
 
 (def .public (tuple generate archive elemsS+)
   (Generator (Tuple Synthesis))
-  (case elemsS+
+  (when elemsS+
     {.#End}
     (///////phase#in (//primitive.text /////synthesis.unit))
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/case.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/when.lux
index 88a7e039e..28599463f 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/case.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/ruby/when.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except case exec let if symbol)
+  [lux (.except when exec let if symbol)
    [abstract
     ["[0]" monad (.only do)]]
    [data
@@ -26,7 +26,7 @@
    ["[1][0]" reference]
    ["/[1]" //
     [synthesis
-     ["[0]" case]]
+     ["[0]" when]]
     ["/[1]" //
      ["[1][0]" generation]
      ["[1][0]" synthesis (.only Synthesis Path)
@@ -166,7 +166,7 @@
                                                   (|> idx .int _.int)))
           (.if simple?
             (_.when (_.= _.nil @temp)
-                    fail!)
+              fail!)
             (_.if (_.= _.nil @temp)
               fail!
               (..push! @temp)))))]
@@ -193,7 +193,7 @@
                     (_.set (list g!continue?) (_.bool true))
                     _.break)))
          (_.when g!continue?
-                 _.next))))
+           _.next))))
 
 (def (alternation in_closure? g!once g!continue? pre! post!)
   (-> Bit LVar LVar Statement Statement Statement)
@@ -208,11 +208,11 @@
 (def (primitive_pattern_matching again pathP)
   (-> (-> Path (Operation Statement))
       (-> Path (Operation (Maybe Statement))))
-  (.case pathP
+  (.when pathP
     {/////synthesis.#Bit_Fork when thenP elseP}
     (do [! ///////phase.monad]
       [then! (again thenP)
-       else! (.case elseP
+       else! (.when elseP
                {.#Some elseP}
                (again elseP)
 
@@ -251,12 +251,12 @@
   (function (again pathP)
     (do ///////phase.monad
       [?output (primitive_pattern_matching again pathP)]
-      (.case ?output
+      (.when ?output
         {.#Some output}
         (in output)
         
         {.#None}
-        (.case pathP
+        (.when pathP
           {/////synthesis.#Then bodyS}
           (statement expression archive bodyS)
 
@@ -269,7 +269,7 @@
           {/////synthesis.#Bit_Fork when thenP elseP}
           (do [! ///////phase.monad]
             [then! (again thenP)
-             else! (.case elseP
+             else! (.when elseP
                      {.#Some elseP}
                      (again elseP)
 
@@ -328,7 +328,7 @@
                                   then!)))
 
           (/////synthesis.!multi_pop nextP)
-          (.let [[extra_pops nextP'] (case.count_pops nextP)]
+          (.let [[extra_pops nextP'] (when.count_pops nextP)]
             (do ///////phase.monad
               [next! (again nextP')]
               (///////phase#in (all _.then
@@ -360,9 +360,9 @@
     (in (all _.then
              (..with_looping in_closure? g!once g!continue?
                pattern_matching!)
-             (_.statement (_.raise (_.string case.pattern_matching_error)))))))
+             (_.statement (_.raise (_.string when.pattern_matching_error)))))))
 
-(def .public (case! in_closure? statement expression archive [valueS pathP])
+(def .public (when! in_closure? statement expression archive [valueS pathP])
   (-> Bit (Generator! [Synthesis Path]))
   (do ///////phase.monad
     [stack_init (expression archive valueS)
@@ -373,10 +373,10 @@
              pattern_matching!
              ))))
 
-(def .public (case statement expression archive case)
+(def .public (when statement expression archive when)
   (-> Phase! (Generator [Synthesis Path]))
-  (|> case
-      (case! true statement expression archive)
+  (|> when
+      (when! true statement expression archive)
       (at ///////phase.monad each
           (|>> [(list)] (_.lambda {.#None})
                (_.apply_lambda (list))))))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme.lux
index cdedd1a3d..e62788463 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme.lux
@@ -13,7 +13,7 @@
   ["[1][0]" primitive]
   ["[1][0]" structure]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" loop]
   ["[1][0]" function]
   ["/[1]" //
@@ -30,7 +30,7 @@
 
 (def .public (generate archive synthesis)
   Phase
-  (case synthesis
+  (when synthesis
     (^.with_template [<tag> <generator>]
       [(<tag> value)
        (//////phase#in (<generator> value))])
@@ -47,12 +47,12 @@
        (<generator> generate archive value)])
     ([////synthesis.variant /structure.variant]
      [////synthesis.tuple /structure.tuple]
-     [////synthesis.branch/let /case.let]
-     [////synthesis.branch/if /case.if]
-     [////synthesis.branch/get /case.get]
+     [////synthesis.branch/let /when.let]
+     [////synthesis.branch/if /when.if]
+     [////synthesis.branch/get /when.get]
      [////synthesis.function/apply /function.apply]
 
-     [////synthesis.branch/case /case.case]
+     [////synthesis.branch/when /when.when]
      [////synthesis.loop/scope /loop.scope]
      [////synthesis.loop/again /loop.again]
      [////synthesis.function/abstraction /function.function])
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/function.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/function.lux
index cbddbab59..5688d5457 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/function.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/function.lux
@@ -17,7 +17,7 @@
  ["[0]" //
   ["[1][0]" runtime (.only Operation Phase Generator)]
   ["[1][0]" reference]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["//[1]" ///
@@ -44,7 +44,7 @@
 (def (with_closure inits function_definition)
   (-> (List Expression) Computation (Operation Computation))
   (///////phase#in
-   (case inits
+   (when inits
      {.#End}
      function_definition
 
@@ -59,7 +59,7 @@
 (def @missing (_.var "missing"))
 
 (def input
-  (|>> ++ //case.register))
+  (|>> ++ //when.register))
 
 (def .public (function expression archive [environment arity bodyS])
   (Generator (Abstraction Synthesis))
@@ -80,7 +80,7 @@
       (_.letrec (list [@self (_.lambda [(list) {.#Some @curried}]
                                        (_.let (list [@num_args (_.length/1 @curried)])
                                          (<| (_.if (|> @num_args (_.=/2 arityO))
-                                               (<| (_.let (list [(//case.register 0) @self]))
+                                               (<| (_.let (list [(//when.register 0) @self]))
                                                    (_.let_values (list [[(|> (list.indices arity)
                                                                              (list#each ..input))
                                                                          {.#None}]
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/loop.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/loop.lux
index d8cf4511e..451de1c90 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/loop.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/loop.lux
@@ -18,12 +18,12 @@
      ["_" scheme]]]]]
  ["[0]" //
   [runtime (.only Operation Phase Generator)]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["/[1]" //
    ["[1][0]" reference]
    ["/[1]" //
     [synthesis
-     ["[0]" case]]
+     ["[0]" when]]
     ["/[1]" //
      ["[0]" synthesis (.only Scope Synthesis)]
      ["[1][0]" generation]
@@ -39,7 +39,7 @@
 
 (def .public (scope expression archive [start initsS+ bodyS])
   (Generator (Scope Synthesis))
-  (case initsS+
+  (when initsS+
     ... function/false/non-independent loop
     {.#End}
     (expression archive bodyS)
@@ -52,7 +52,7 @@
                (expression archive bodyS))]
       (in (_.letrec (list [@scope (_.lambda [(|> initsS+
                                                  list.enumeration
-                                                 (list#each (|>> product.left (n.+ start) //case.register)))
+                                                 (list#each (|>> product.left (n.+ start) //when.register)))
                                              {.#None}]
                                             bodyO)])
                     (_.apply initsO+ @scope))))))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/runtime.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/runtime.lux
index 31803cfab..e0eb242ec 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/runtime.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/runtime.lux
@@ -81,7 +81,7 @@
       (macro.with_symbols [g!_]
         (let [runtime (code.local (///reference.artifact [..module_id runtime_id]))
               runtime_name (` (_.var (, (code.text (%.code runtime)))))]
-          (case declaration
+          (when declaration
             {.#Left name}
             (let [g!name (code.local name)]
               (in (list (` (def .public (, g!name)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/structure.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/structure.lux
index e98aa8ff4..526b833ff 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/structure.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/structure.lux
@@ -20,7 +20,7 @@
 
 (def .public (tuple expression archive elemsS+)
   (Generator (Tuple Synthesis))
-  (case elemsS+
+  (when elemsS+
     {.#End}
     (///////phase#in (//primitive.text /////synthesis.unit))
 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/case.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/when.lux
index a1f679836..b70ccef33 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/case.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/generation/scheme/when.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except case let if)
+  [lux (.except when let if)
    [abstract
     ["[0]" monad (.only do)]]
    [data
@@ -27,7 +27,7 @@
    ["[1][0]" reference]
    ["/[1]" //
     ["[1][0]" synthesis
-     ["[1]/[0]" case]]
+     ["[1]/[0]" when]]
     ["/[1]" //
      ["[1][0]" synthesis (.only Member Synthesis Path)]
      ["[1][0]" generation]
@@ -67,7 +67,7 @@
   (do ///////phase.monad
     [valueO (expression archive valueS)]
     (in (list#mix (function (_ side source)
-                    (.let [method (.case side
+                    (.let [method (.when side
                                     (^.with_template [<side> <accessor>]
                                       [(<side> lefts)
                                        (<accessor> (_.int (.int lefts)))])
@@ -130,7 +130,7 @@
 (def (pattern_matching' expression archive)
   (Generator Path)
   (function (again pathP)
-    (.case pathP
+    (.when pathP
       {/////synthesis.#Then bodyS}
       (expression archive bodyS)
 
@@ -143,7 +143,7 @@
       {/////synthesis.#Bit_Fork when thenP elseP}
       (do [! ///////phase.monad]
         [then! (again thenP)
-         else! (.case elseP
+         else! (.when elseP
                  {.#Some elseP}
                  (again elseP)
 
@@ -216,7 +216,7 @@
       (try_pm (_.raise/1 (_.string "Invalid expression for pattern-matching.")))
       (pattern_matching' expression archive pathP)))
 
-(def .public (case expression archive [valueS pathP])
+(def .public (when expression archive [valueS pathP])
   (Generator [Synthesis Path])
   (do [! ///////phase.monad]
     [valueO (expression archive valueS)]
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis.lux
index b21dbdaae..fba249351 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis.lux
@@ -15,7 +15,7 @@
      ["^" pattern]]]]]
  ["[0]" /
   ["[1][0]" function]
-  ["[1][0]" case]
+  ["[1][0]" when]
   ["[1][0]" variable]
   ["/[1]" //
    ["[1][0]" extension]
@@ -32,7 +32,7 @@
 
 (def (simple analysis)
   (-> ///simple.Simple /simple.Simple)
-  (case analysis
+  (when analysis
     {///simple.#Unit}
     {/simple.#Text /.unit}
     
@@ -53,7 +53,7 @@
 (def (optimization archive)
   Phase
   (function (optimization' analysis)
-    (case analysis
+    (when analysis
       {///analysis.#Simple analysis'}
       (phase#in {/.#Simple (..simple analysis')})
 
@@ -62,7 +62,7 @@
 
       {///analysis.#Structure structure}
       (/.with_currying? false
-        (case structure
+        (when structure
           {///complex.#Variant variant}
           (do phase.monad
             [valueS (optimization' (the ///complex.#value variant))]
@@ -73,9 +73,9 @@
               (monad.each phase.monad optimization')
               (phase#each (|>> /.tuple)))))
       
-      {///analysis.#Case inputA branchesAB+}
+      {///analysis.#When inputA branchesAB+}
       (/.with_currying? false
-        (/case.synthesize optimization branchesAB+ archive inputA))
+        (/when.synthesize optimization branchesAB+ archive inputA))
 
       (///analysis.no_op value)
       (optimization' value)
@@ -92,7 +92,7 @@
         (function (_ state)
           (|> (//extension.apply archive optimization [name args])
               (phase.result' state)
-              (pipe.case
+              (pipe.when
                 {try.#Success output}
                 {try.#Success output}
                 
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/function.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/function.lux
index e9507024a..c1a6184d1 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/function.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/function.lux
@@ -59,7 +59,7 @@
         [funcS (phase archive funcA)
          argsS (monad.each ! (phase archive) argsA)]
         (with_expansions [<apply> (these (/.function/apply [funcS argsS]))]
-          (case funcS
+          (when funcS
             (/.function/abstraction functionS)
             (if (n.= (the /.#arity functionS)
                      (list.size argsS))
@@ -69,7 +69,7 @@
                         (//loop.optimization true locals argsS)
                         (maybe#each (is (-> [Nat (List Synthesis) Synthesis] Synthesis)
                                         (function (_ [start inits iteration])
-                                          (case iteration
+                                          (when iteration
                                             (/.loop/scope [start' inits' output])
                                             (if (and (n.= start start')
                                                      (list.empty? inits'))
@@ -89,7 +89,7 @@
 
 (def (find_foreign environment register)
   (-> (Environment Synthesis) Register (Operation Synthesis))
-  (case (list.item register environment)
+  (when (list.item register environment)
     {.#Some aliased}
     (phase#in aliased)
 
@@ -98,7 +98,7 @@
 
 (def (grow_path grow path)
   (-> (-> Synthesis (Operation Synthesis)) Path (Operation Path))
-  (case path
+  (when path
     {/.#Bind register}
     (phase#in {/.#Bind (++ register)})
 
@@ -110,16 +110,16 @@
          (in {<tag> left' right'}))])
     ([/.#Alt] [/.#Seq])
 
-    {/.#Bit_Fork when then else}
+    {/.#Bit_Fork test then else}
     (do [! phase.monad]
       [then (grow_path grow then)
-       else (case else
+       else (when else
               {.#Some else}
               (at ! each (|>> {.#Some}) (grow_path grow else))
 
               {.#None}
               (in {.#None}))]
-      (in {/.#Bit_Fork when then else}))
+      (in {/.#Bit_Fork test then else}))
     
     (^.with_template [<tag>]
       [{<tag> [[test then] elses]}
@@ -145,9 +145,9 @@
 
 (def (grow environment expression)
   (-> (Environment Synthesis) Synthesis (Operation Synthesis))
-  (case expression
+  (when expression
     {/.#Structure structure}
-    (case structure
+    (when structure
       {////analysis/complex.#Variant [lefts right? subS]}
       (|> subS
           (grow environment)
@@ -162,9 +162,9 @@
     (phase#in (/.function/apply [expression (list (/.variable/local 1))]))
     
     {/.#Reference reference}
-    (case reference
+    (when reference
       {////reference.#Variable variable}
-      (case variable
+      (when variable
         {////reference/variable.#Local register}
         (phase#in (/.variable/local (++ register)))
         
@@ -175,9 +175,9 @@
       (phase#in expression))
     
     {/.#Control control}
-    (case control
+    (when control
       {/.#Branch branch}
-      (case branch
+      (when branch
         {/.#Exec [this that]}
         (do phase.monad
           [this (grow environment this)
@@ -202,14 +202,14 @@
           [inputS' (grow environment inputS)]
           (in (/.branch/get [members inputS'])))
         
-        {/.#Case [inputS pathS]}
+        {/.#When [inputS pathS]}
         (do phase.monad
           [inputS' (grow environment inputS)
            pathS' (grow_path (grow environment) pathS)]
-          (in (/.branch/case [inputS' pathS']))))
+          (in (/.branch/when [inputS' pathS']))))
       
       {/.#Loop loop}
-      (case loop
+      (when loop
         {/.#Scope [start initsS+ iterationS]}
         (do [! phase.monad]
           [initsS+' (monad.each ! (grow environment) initsS+)
@@ -222,11 +222,11 @@
             (phase#each (|>> /.loop/again))))
       
       {/.#Function function}
-      (case function
+      (when function
         {/.#Abstraction [_env _arity _body]}
         (do [! phase.monad]
           [_env' (monad.each !
-                             (|>> (pipe.case
+                             (|>> (pipe.when
                                     {/.#Reference {////reference.#Variable {////reference/variable.#Foreign register}}}
                                     (..find_foreign environment register)
 
@@ -239,7 +239,7 @@
         (do [! phase.monad]
           [funcS (grow environment funcS)
            argsS+ (monad.each ! (grow environment) argsS+)]
-          (in (/.function/apply (case funcS
+          (in (/.function/apply (when funcS
                                   (/.function/apply [(..self_reference) pre_argsS+])
                                   [(..self_reference)
                                    (list#composite pre_argsS+ argsS+)]
@@ -264,7 +264,7 @@
              (/.with_locals 2
                (phase archive bodyA)))
      abstraction (is (Operation Abstraction)
-                     (case bodyS
+                     (when bodyS
                        (/.function/abstraction [env' down_arity' bodyS'])
                        (|> bodyS'
                            (grow env')
@@ -281,7 +281,7 @@
     (in (/.function/abstraction
          (if currying?
            abstraction
-           (case (//loop.optimization false 1 (list) abstraction)
+           (when (//loop.optimization false 1 (list) abstraction)
              {.#Some [startL initsL bodyL]}
              [/.#environment environment
               /.#arity (the /.#arity abstraction)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/loop.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/loop.lux
index c967930bf..0ae8912f8 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/loop.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/loop.lux
@@ -33,7 +33,7 @@
 (def (path_optimization body_optimization offset)
   (-> (Transform Synthesis) Register (Transform Path))
   (function (again path)
-    (case path
+    (when path
       {/.#Bind register}
       {.#Some {/.#Bind (register_optimization offset register)}}
 
@@ -45,16 +45,16 @@
            (in {<tag> left' right'}))])
       ([/.#Alt] [/.#Seq])
 
-      {/.#Bit_Fork when then else}
+      {/.#Bit_Fork test then else}
       (do [! maybe.monad]
         [then (again then)
-         else (case else
+         else (when else
                 {.#Some else}
                 (at ! each (|>> {.#Some}) (again else))
 
                 {.#None}
                 (in {.#None}))]
-        (in {/.#Bit_Fork when then else}))
+        (in {/.#Bit_Fork test then else}))
       
       (^.with_template [<tag>]
         [{<tag> [[test then] elses]}
@@ -82,12 +82,12 @@
   (-> Bit Register (Environment Synthesis) Arity (Transform Synthesis))
   (loop (again [return? true
                 expr expr])
-    (case expr
+    (when expr
       {/.#Simple _}
       {.#Some expr}
 
       {/.#Structure structure}
-      (case structure
+      (when structure
         {analysis/complex.#Variant variant}
         (do maybe.monad
           [value' (|> variant (the analysis/complex.#value) (again false))]
@@ -101,7 +101,7 @@
             (maybe#each (|>> /.tuple))))
 
       {/.#Reference reference}
-      (case reference
+      (when reference
         {reference.#Variable (variable.self)}
         (if true_loop?
           {.#None}
@@ -118,11 +118,11 @@
           (list.item register scope_environment)
           {.#Some expr}))
 
-      (/.branch/case [input path])
+      (/.branch/when [input path])
       (do maybe.monad
         [input' (again false input)
          path' (path_optimization (again return?) offset path)]
-        (in (|> path' [input'] /.branch/case)))
+        (in (|> path' [input'] /.branch/when)))
 
       (/.branch/exec [this that])
       (do maybe.monad
@@ -174,7 +174,7 @@
         (with_expansions [<application> (these (do !
                                                  [abstraction' (again false abstraction)]
                                                  (in (/.function/apply [abstraction' arguments']))))]
-          (case abstraction
+          (when abstraction
             {/.#Reference {reference.#Variable (variable.self)}}
             (if (and return?
                      (n.= arity (list.size arguments)))
@@ -193,7 +193,7 @@
           [input (again false input)
            matches (monad.each !
                                (function (_ match)
-                                 (case match
+                                 (when match
                                    {/.#Structure {analysis/complex.#Tuple (list when then)}}
                                    (do !
                                      [when (again false when)
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/variable.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/variable.lux
index f6ef820af..0f0d88bdd 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/variable.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/variable.lux
@@ -43,7 +43,7 @@
 (def (remove_local_from_path remove_local redundant)
   (-> (Remover Synthesis) (Remover Path))
   (function (again path)
-    (case path
+    (when path
       {/.#Seq {/.#Bind register}
               post}
       (if (n.= redundant register)
@@ -101,7 +101,7 @@
 
 (def (remove_local_from_variable redundant variable)
   (Remover Variable)
-  (case variable
+  (when variable
     {variable.#Local register}
     {variable.#Local (..prune redundant register)}
     
@@ -111,12 +111,12 @@
 (def (remove_local redundant)
   (Remover Synthesis)
   (function (again synthesis)
-    (case synthesis
+    (when synthesis
       {/.#Simple _}
       synthesis
       
       {/.#Structure structure}
-      {/.#Structure (case structure
+      {/.#Structure (when structure
                       {analysis/complex.#Variant [lefts right value]}
                       {analysis/complex.#Variant [lefts right (again value)]}
                       
@@ -124,7 +124,7 @@
                       {analysis/complex.#Tuple (list#each again tuple)})}
       
       {/.#Reference reference}
-      (case reference
+      (when reference
         {reference.#Variable variable}
         (/.variable (..remove_local_from_variable redundant variable))
 
@@ -132,9 +132,9 @@
         synthesis)
       
       {/.#Control control}
-      {/.#Control (case control
+      {/.#Control (when control
                     {/.#Branch branch}
-                    {/.#Branch (case branch
+                    {/.#Branch (when branch
                                  {/.#Exec this that}
                                  {/.#Exec (again this)
                                           (again that)}
@@ -150,11 +150,11 @@
                                  {/.#Get path record}
                                  {/.#Get path (again record)}
                                  
-                                 {/.#Case input path}
-                                 {/.#Case (again input) (remove_local_from_path remove_local redundant path)})}
+                                 {/.#When input path}
+                                 {/.#When (again input) (remove_local_from_path remove_local redundant path)})}
                     
                     {/.#Loop loop}
-                    {/.#Loop (case loop
+                    {/.#Loop (when loop
                                {/.#Scope [start inits iteration]}
                                {/.#Scope [(..prune redundant start)
                                           (list#each again inits)
@@ -164,7 +164,7 @@
                                {/.#Again (list#each again resets)})}
 
                     {/.#Function function}
-                    {/.#Function (case function
+                    {/.#Function (when function
                                    {/.#Abstraction [environment arity body]}
                                    {/.#Abstraction [(list#each again environment)
                                                     arity
@@ -205,7 +205,7 @@
 (def (list_optimization optimization)
   (All (_ a) (-> (Optimization a) (Optimization (List a))))
   (function (again [redundancy values])
-    (case values
+    (when values
       {.#End}
       {try.#Success [redundancy
                      values]}
@@ -228,7 +228,7 @@
 
 (def (declare register redundancy)
   (-> Register Redundancy (Try Redundancy))
-  (case (dictionary.value register redundancy)
+  (when (dictionary.value register redundancy)
     {.#None}
     {try.#Success (dictionary.has register ..redundant! redundancy)}
     
@@ -237,7 +237,7 @@
 
 (def (observe register redundancy)
   (-> Register Redundancy (Try Redundancy))
-  (case (dictionary.value register redundancy)
+  (when (dictionary.value register redundancy)
     {.#None}
     (exception.except ..unknown_register [register])
     
@@ -255,16 +255,16 @@
 (def (path_optimization optimization)
   (-> (Optimization Synthesis) (Optimization Path))
   (function (again [redundancy path])
-    (case path
+    (when path
       (^.or {/.#Pop}
             {/.#Access _})
       {try.#Success [redundancy
                      path]}
 
-      {/.#Bit_Fork when then else}
+      {/.#Bit_Fork test then else}
       (do [! try.monad]
         [[redundancy then] (again [redundancy then])
-         [redundancy else] (case else
+         [redundancy else] (when else
                              {.#Some else}
                              (at ! each
                                  (function (_ [redundancy else])
@@ -273,7 +273,7 @@
 
                              {.#None}
                              (in [redundancy {.#None}]))]
-        (in [redundancy {/.#Bit_Fork when then else}]))
+        (in [redundancy {/.#Bit_Fork test then else}]))
       
       (^.with_template [<tag> <type>]
         [{<tag> [[test then] elses]}
@@ -334,12 +334,12 @@
   (Optimization Synthesis)
   (with_expansions [<no_op> (these {try.#Success [redundancy
                                                   synthesis]})]
-    (case synthesis
+    (when synthesis
       {/.#Simple _}
       <no_op>
       
       {/.#Structure structure}
-      (case structure
+      (when structure
         {analysis/complex.#Variant [lefts right value]}
         (do try.monad
           [[redundancy value] (optimization' [redundancy value])]
@@ -353,9 +353,9 @@
                {/.#Structure {analysis/complex.#Tuple tuple}}])))
       
       {/.#Reference reference}
-      (case reference
+      (when reference
         {reference.#Variable variable}
-        (case variable
+        (when variable
           {variable.#Local register}
           (do try.monad
             [redundancy (..observe register redundancy)]
@@ -368,9 +368,9 @@
         <no_op>)
       
       {/.#Control control}
-      (case control
+      (when control
         {/.#Branch branch}
-        (case branch
+        (when branch
           {/.#Exec this that}
           (do try.monad
             [[redundancy this] (optimization' [redundancy this])
@@ -405,15 +405,15 @@
             (in [redundancy
                  {/.#Control {/.#Branch {/.#Get path record}}}]))
           
-          {/.#Case input path}
+          {/.#When input path}
           (do try.monad
             [[redundancy input] (optimization' [redundancy input])
              [redundancy path] (..path_optimization optimization' [redundancy path])]
             (in [redundancy
-                 {/.#Control {/.#Branch {/.#Case input path}}}])))
+                 {/.#Control {/.#Branch {/.#When input path}}}])))
         
         {/.#Loop loop}
-        (case loop
+        (when loop
           {/.#Scope [start inits iteration]}
           (do try.monad
             [[redundancy inits] (..list_optimization optimization' [redundancy inits])
@@ -429,7 +429,7 @@
                  {/.#Control {/.#Loop {/.#Again resets}}}])))
 
         {/.#Function function}
-        (case function
+        (when function
           {/.#Abstraction [environment arity body]}
           (do [! try.monad]
             [[redundancy environment] (..list_optimization optimization' [redundancy environment])
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/case.lux b/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/when.lux
index d6d6f31ed..c41a41da0 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/case.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/phase/synthesis/when.lux
@@ -44,9 +44,9 @@
 
 (def (path' pattern end? thenC)
   (-> Pattern Bit (Operation Path) (Operation Path))
-  (case pattern
+  (when pattern
     {///pattern.#Simple simple}
-    (case simple
+    (when simple
       {///simple.#Unit}
       thenC
 
@@ -75,13 +75,15 @@
     (<| (///#each (|>> {/.#Seq {/.#Access {/access.#Side [/side.#lefts lefts
                                                           /side.#right? right?]}}}))
         (path' value_pattern end?)
-        (pipe.when [(pipe.new (not end?) [])] [(///#each ..clean_up)])
+        (pipe.if [(pipe.new (not end?) [])]
+          [(///#each ..clean_up)]
+          [])
         thenC)
 
     {///pattern.#Complex {///complex.#Tuple tuple}}
     (let [tuple::last (-- (list.size tuple))]
       (list#mix (function (_ [tuple::lefts tuple::member] nextC)
-                  (.case tuple::member
+                  (.when tuple::member
                     {///pattern.#Simple {///simple.#Unit}}
                     nextC
 
@@ -93,7 +95,9 @@
                                                                                                tuple::lefts)
                                                                               /member.#right? right?]}}}))
                           (path' tuple::member end?')
-                          (pipe.when [(pipe.new (not end?') [])] [(///#each ..clean_up)])
+                          (pipe.if [(pipe.new (not end?') [])]
+                            [(///#each ..clean_up)]
+                            [])
                           nextC))))
                 thenC
                 (list.reversed (list.enumeration tuple))))
@@ -110,7 +114,7 @@
   (if (at equivalence = new_test old_test)
     [[old_test (weave new_then old_then)] old_tail]
     [[old_test old_then]
-     (case old_tail
+     (when old_tail
        {.#End}
        (list [new_test new_then])
        
@@ -126,7 +130,7 @@
 (def (weave new old)
   (-> Path Path Path)
   (with_expansions [<default> (these {/.#Alt old new})]
-    (case [new old]
+    (when [new old]
       [_
        {/.#Alt old_left old_right}]
       {/.#Alt old_left
@@ -134,7 +138,7 @@
 
       [{/.#Seq preN postN}
        {/.#Seq preO postO}]
-      (case (weave preN preO)
+      (when (weave preN preO)
         {/.#Alt _}
         <default>
 
@@ -149,7 +153,7 @@
       (if (bit#= new_when old_when)
         {/.#Bit_Fork old_when
                      (weave new_then old_then)
-                     (case [new_else old_else]
+                     (when [new_else old_else]
                        [{.#None} {.#None}]
                        {.#None}
 
@@ -160,13 +164,13 @@
                        [{.#Some new_else} {.#Some old_else}]
                        {.#Some (weave new_else old_else)})}
         {/.#Bit_Fork old_when
-                     (case new_else
+                     (when new_else
                        {.#None}
                        old_then
 
                        {.#Some new_else}
                        (weave new_else old_then))
-                     {.#Some (case old_else
+                     {.#Some (when old_else
                                {.#None}
                                new_then
 
@@ -212,12 +216,12 @@
                                                           (-- lefts)
                                                           lefts)
                                          /member.#right? right?]))]
-      (case patterns
+      (when patterns
         {.#End}
         <failure>
 
         {.#Item head tail}
-        (case head
+        (when head
           {///pattern.#Simple {///simple.#Unit}}
           <continue>
           
@@ -227,7 +231,7 @@
             <continue>)
 
           {///pattern.#Complex {///complex.#Tuple sub_patterns}}
-          (case (get sub_patterns @selection)
+          (when (get sub_patterns @selection)
             {.#End}
             <continue>
 
@@ -237,12 +241,12 @@
           _
           <failure>)))))
 
-(def .public (synthesize_case synthesize archive input [[headP headA] tailPA+])
+(def .public (synthesize_when synthesize archive input [[headP headA] tailPA+])
   (-> Phase Archive Synthesis Match (Operation Synthesis))
   (do [! ///.monad]
     [headSP (path archive synthesize headP headA)
      tailSP+ (monad.each ! (product.uncurried (path archive synthesize)) tailPA+)]
-    (in (/.branch/case [input (list#mix weave headSP tailSP+)]))))
+    (in (/.branch/when [input (list#mix weave headSP tailSP+)]))))
 
 (def !masking
   (template (_ <variable> <output>)
@@ -284,12 +288,12 @@
 
 (def .public (synthesize_get synthesize archive input patterns @member)
   (-> Phase Archive Synthesis (///complex.Tuple Pattern) Register (Operation Synthesis))
-  (case (..get patterns @member)
+  (when (..get patterns @member)
     {.#End}
-    (..synthesize_case synthesize archive input (!get patterns @member))
+    (..synthesize_when synthesize archive input (!get patterns @member))
 
     path
-    (case input
+    (when input
       (/.branch/get [sub_path sub_input])
       (///#in (/.branch/get [(list#composite path sub_path) sub_input]))
 
@@ -300,13 +304,13 @@
   (-> Phase Match Phase)
   (do [! ///.monad]
     [inputS (synthesize^ archive inputA)]
-    (case [headB tailB+]
+    (when [headB tailB+]
       (!masking @variable @output)
       (..synthesize_masking synthesize^ archive inputS @variable @output)
 
       [[(///pattern.unit) body]
        {.#End}]
-      (case inputA
+      (when inputA
         (^.or {///analysis.#Simple _}
               {///analysis.#Structure _}
               {///analysis.#Reference _})
@@ -334,11 +338,11 @@
       (..synthesize_get synthesize^ archive inputS patterns @member)
       
       match
-      (..synthesize_case synthesize^ archive inputS match))))
+      (..synthesize_when synthesize^ archive inputS match))))
 
 (def .public (count_pops path)
   (-> Path [Nat Path])
-  (case path
+  (when path
     (/.path/seq {/.#Pop} path')
     (let [[pops post_pops] (count_pops path')]
       [(++ pops) post_pops])
@@ -369,7 +373,7 @@
   (-> Path Storage)
   (loop (for_path [path path
                    path_storage ..empty])
-    (case path
+    (when path
       (^.or {/.#Pop}
             {/.#Access Access})
       path_storage
@@ -379,7 +383,7 @@
                path_storage)
 
       {/.#Bit_Fork _ default otherwise}
-      (|> (case otherwise
+      (|> (when otherwise
             {.#None}
             path_storage
             
@@ -401,7 +405,7 @@
       (/.path/then bodyS)
       (loop (for_synthesis [bodyS bodyS
                             synthesis_storage path_storage])
-        (case bodyS
+        (when bodyS
           (^.or {/.#Simple _}
                 (/.constant _))
           synthesis_storage
@@ -426,7 +430,7 @@
           (/.function/abstraction [environment arity bodyS])
           (list#mix for_synthesis synthesis_storage environment)
 
-          (/.branch/case [inputS pathS])
+          (/.branch/when [inputS pathS])
           (revised #dependencies
                    (set.union (the #dependencies (for_path pathS synthesis_storage)))
                    (for_synthesis inputS synthesis_storage))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/program.lux b/stdlib/source/library/lux/meta/compiler/language/lux/program.lux
index 502922736..864a8f817 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/program.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/program.lux
@@ -43,7 +43,7 @@
                                     [id (archive.id module archive)
                                      [_module output registry] (archive.find module archive)]
                                     (in [[module id] registry])))))]
-    (case (list.one (function (_ [[module module_id] registry])
+    (when (list.one (function (_ [[module module_id] registry])
                       (do maybe.monad
                         [program_id (registry.id ..name registry)]
                         (in [module_id program_id])))
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/syntax.lux b/stdlib/source/library/lux/meta/compiler/language/lux/syntax.lux
index 86d0cc16a..bbf548818 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/syntax.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/syntax.lux
@@ -215,7 +215,7 @@
 
 (def !letE
   (template (_ <binding> <computation> <body>)
-    [(case <computation>
+    [(when <computation>
        {.#Right <binding>}
        <body>
 
@@ -251,7 +251,7 @@
          (Either [Source Text] [Source Code]))
      (loop (again [source (is Source [(!forward 1 where) offset source_code])
                    stack (is (List Code) {.#End})])
-       (case (parse source)
+       (when (parse source)
          {.#Right [source' top]}
          (again source' {.#Item top stack})
          
@@ -271,7 +271,7 @@
 
 (def !guarantee_no_new_lines
   (template (_ where offset source_code content body)
-    [(case ("lux text index" 0 (static text.new_line) content)
+    [(when ("lux text index" 0 (static text.new_line) content)
        {.#None}
        body
 
@@ -281,7 +281,7 @@
 
 (def (text_parser where offset source_code)
   (-> Location Offset Text (Either [Source Text] [Source Code]))
-  (case ("lux text index" offset (static ..text_delimiter) source_code)
+  (when ("lux text index" offset (static ..text_delimiter) source_code)
     {.#Some g!end}
     (<| (let [g!content (!clip offset g!end source_code)])
         (!guarantee_no_new_lines where offset source_code g!content)
@@ -348,7 +348,7 @@
 
 (def !number_output
   (template (_ <source_code> <start> <end> <codec> <tag>)
-    [(case (|> <source_code>
+    [(when (|> <source_code>
                (!clip <start> <end>)
                (text.replaced ..digit_separator "")
                (at <codec> decoded))
@@ -562,7 +562,7 @@
                     ... It's either a Rev, a symbol, or a comment.
                     (with_expansions [<rev_parser> (rev_parser source_code//size offset/0 where (!++ offset/1) source_code)
                                       <short_symbol_parser> (!short_symbol_parser source_code//size current_module [where offset/1 source_code] where .#Symbol)
-                                      <comment_parser> (case ("lux text index" (!++ offset/1) (static text.new_line) source_code)
+                                      <comment_parser> (when ("lux text index" (!++ offset/1) (static text.new_line) source_code)
                                                          {.#Some end}
                                                          (again (!vertical where end source_code))
                                                          
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/synthesis.lux b/stdlib/source/library/lux/meta/compiler/language/lux/synthesis.lux
index 735da0f51..29b3604b8 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/synthesis.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/synthesis.lux
@@ -98,7 +98,7 @@
    {#Let s Register s}
    {#If s s s}
    {#Get (List Member) s}
-   {#Case s (Path' s)}))
+   {#When s (Path' s)}))
 
 (type .public (Scope s)
   (Record
@@ -274,7 +274,7 @@
              {<tag>}
              content)]))]
 
-  [branch/case          ..#Branch   ..#Case]
+  [branch/when          ..#Branch   ..#When]
   [branch/exec          ..#Branch   ..#Exec]
   [branch/let           ..#Branch   ..#Let]
   [branch/if            ..#Branch   ..#If]
@@ -289,16 +289,16 @@
 
 (def .public (%path' %then value)
   (All (_ a) (-> (Format a) (Format (Path' a))))
-  (case value
+  (when value
     {#Pop}
     "_"
 
-    {#Bit_Fork when then else}
+    {#Bit_Fork test then else}
     (format "(?"
-            " " (%.bit when) " " (%path' %then then)
-            (case else
+            " " (%.bit test) " " (%path' %then then)
+            (when else
               {.#Some else}
-              (format " " (%.bit (not when)) " " (%path' %then else))
+              (format " " (%.bit (not test)) " " (%path' %then else))
 
               {.#None}
               "")
@@ -333,12 +333,12 @@
 
 (def .public (%synthesis value)
   (Format Synthesis)
-  (case value
+  (when value
     {#Simple it}
     (/simple.format it)
 
     {#Structure structure}
-    (case structure
+    (when structure
       {analysis/complex.#Variant [lefts right? content]}
       (|> (%synthesis content)
           (format (%.nat lefts) " " (%.bit right?) " ")
@@ -354,9 +354,9 @@
     (reference.format reference)
 
     {#Control control}
-    (case control
+    (when control
       {#Function function}
-      (case function
+      (when function
         {#Abstraction [environment arity body]}
         (let [environment' (|> environment
                                (list#each %synthesis)
@@ -373,7 +373,7 @@
             (text.enclosed ["(" ")"])))
 
       {#Branch branch}
-      (case branch
+      (when branch
         {#Exec this that}
         (|> (format (%synthesis this) " " (%synthesis that))
             (text.enclosed ["{#exec " "}"]))
@@ -392,12 +392,12 @@
                     " " (%synthesis record))
             (text.enclosed ["{#get " "}"]))
         
-        {#Case input path}
+        {#When input path}
         (|> (format (%synthesis input) " " (%path' %synthesis path))
-            (text.enclosed ["{#case " "}"])))
+            (text.enclosed ["{#when " "}"])))
       
       {#Loop loop}
-      (case loop
+      (when loop
         {#Scope scope}
         (|> (format (%.nat (the #start scope))
                     " " (|> (the #inits scope)
@@ -427,7 +427,7 @@
   (All (_ a) (-> (Equivalence a) (Equivalence (Path' a))))
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        [{#Pop} {#Pop}]
        true
 
@@ -473,7 +473,7 @@
      (..path'_equivalence (at super equivalence)))
    
    (def (hash value)
-     (case value
+     (when value
        {#Pop}
        2
 
@@ -491,9 +491,9 @@
 
        (^.with_template [<factor> <tag> <hash>]
          [{<tag> item}
-          (let [case_hash (product.hash <hash>
+          (let [when_hash (product.hash <hash>
                                         (path'_hash super))
-                item_hash (product.hash case_hash (list.hash case_hash))]
+                item_hash (product.hash when_hash (list.hash when_hash))]
             (n.* <factor> (at item_hash hash item)))])
        ([11 #I64_Fork i64.hash]
         [13 #F64_Fork f.hash]
@@ -515,7 +515,7 @@
   (All (_ a) (-> (Equivalence a) (Equivalence (Branch a))))
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        [{#Let [reference_input reference_register reference_body]}
         {#Let [sample_input sample_register sample_body]}]
        (and (#= reference_input sample_input)
@@ -533,8 +533,8 @@
        (and (at (list.equivalence /member.equivalence) = reference_path sample_path)
             (#= reference_record sample_record))
        
-       [{#Case [reference_input reference_path]}
-        {#Case [sample_input sample_path]}]
+       [{#When [reference_input reference_path]}
+        {#When [sample_input sample_path]}]
        (and (#= reference_input sample_input)
             (at (path'_equivalence #=) = reference_path sample_path))
        
@@ -548,7 +548,7 @@
      (..branch_equivalence (at super equivalence)))
    
    (def (hash value)
-     (case value
+     (when value
        {#Exec this that}
        (all n.* 2
             (at super hash this)
@@ -571,7 +571,7 @@
             (at (list.hash /member.hash) hash path)
             (at super hash record))
        
-       {#Case [input path]}
+       {#When [input path]}
        (all n.* 11
             (at super hash input)
             (at (..path'_hash super) hash path))
@@ -581,7 +581,7 @@
   (All (_ a) (-> (Equivalence a) (Equivalence (Loop a))))
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        [{#Scope [reference_start reference_inits reference_iteration]}
         {#Scope [sample_start sample_inits sample_iteration]}]
        (and (n.= reference_start sample_start)
@@ -601,7 +601,7 @@
      (..loop_equivalence (at super equivalence)))
    
    (def (hash value)
-     (case value
+     (when value
        {#Scope [start inits iteration]}
        (all n.* 2
             (at n.hash hash start)
@@ -617,7 +617,7 @@
   (All (_ a) (-> (Equivalence a) (Equivalence (Function a))))
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        [{#Abstraction [reference_environment reference_arity reference_body]}
         {#Abstraction [sample_environment sample_arity sample_body]}]
        (and (at (list.equivalence #=) = reference_environment sample_environment)
@@ -639,7 +639,7 @@
      (..function_equivalence (at super equivalence)))
    
    (def (hash value)
-     (case value
+     (when value
        {#Abstraction [environment arity body]}
        (all n.* 2
             (at (list.hash super) hash environment)
@@ -656,7 +656,7 @@
   (All (_ a) (-> (Equivalence a) (Equivalence (Control a))))
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        (^.with_template [<tag> <equivalence>]
          [[{<tag> reference} {<tag> sample}]
           (at (<equivalence> #=) = reference sample)])
@@ -674,7 +674,7 @@
      (..control_equivalence (at super equivalence)))
 
    (def (hash value)
-     (case value
+     (when value
        (^.with_template [<factor> <tag> <hash>]
          [{<tag> value}
           (n.* <factor> (at (<hash> super) hash value))])
@@ -687,7 +687,7 @@
   (Equivalence Synthesis)
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        (^.with_template [<tag> <equivalence>]
          [[{<tag> reference'} {<tag> sample'}]
           (at <equivalence> = reference' sample')])
@@ -711,7 +711,7 @@
 
    (def (hash value)
      (let [again_hash [..equivalence hash]]
-       (case value
+       (when value
          (^.with_template [<tag> <hash>]
            [{<tag> value}
             (at <hash> hash value)])
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/synthesis/access.lux b/stdlib/source/library/lux/meta/compiler/language/lux/synthesis/access.lux
index f599f4d90..fc1d14e8f 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/synthesis/access.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/synthesis/access.lux
@@ -19,7 +19,7 @@
 
 (def .public (format it)
   (Format Access)
-  (case it
+  (when it
     {#Side it}
     (/side.format it)
     
diff --git a/stdlib/source/library/lux/meta/compiler/language/lux/synthesis/simple.lux b/stdlib/source/library/lux/meta/compiler/language/lux/synthesis/simple.lux
index 738ea9b76..a44021d1f 100644
--- a/stdlib/source/library/lux/meta/compiler/language/lux/synthesis/simple.lux
+++ b/stdlib/source/library/lux/meta/compiler/language/lux/synthesis/simple.lux
@@ -29,7 +29,7 @@
 
 (def .public (format it)
   (%.Format Simple)
-  (case it
+  (when it
     (^.with_template [<pattern> <format>]
       [{<pattern> value}
        (<format> value)])
@@ -44,7 +44,7 @@
   (Equivalence Simple)
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        (^.with_template [<tag> <eq> <format>]
          [[{<tag> reference'} {<tag> sample'}]
           (<eq> reference' sample')])
@@ -64,7 +64,7 @@
    (def equivalence ..equivalence)
 
    (def hash
-     (|>> (pipe.case
+     (|>> (pipe.when
             (^.with_template [<factor> <tag> <hash>]
               [{<tag> value'}
                (n.* <factor>  (at <hash> hash value'))])
diff --git a/stdlib/source/library/lux/meta/compiler/meta/archive.lux b/stdlib/source/library/lux/meta/compiler/meta/archive.lux
index a67b84f92..bcbdcaff4 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/archive.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/archive.lux
@@ -89,7 +89,7 @@
   (def .public (id module archive)
     (-> descriptor.Module Archive (Try module.ID))
     (let [(open "/[0]") (representation archive)]
-      (case (dictionary.value module /#resolver)
+      (when (dictionary.value module /#resolver)
         {.#Some [id _]}
         {try.#Success id}
         
@@ -100,7 +100,7 @@
   (def .public (reserve module archive)
     (-> descriptor.Module Archive (Try [module.ID Archive]))
     (let [(open "/[0]") (representation archive)]
-      (case (dictionary.value module /#resolver)
+      (when (dictionary.value module /#resolver)
         {.#Some _}
         (exception.except ..module_has_already_been_reserved [module])
         
@@ -115,7 +115,7 @@
   (def .public (has module entry archive)
     (-> descriptor.Module (Entry Any) Archive (Try Archive))
     (let [(open "/[0]") (representation archive)]
-      (case (dictionary.value module /#resolver)
+      (when (dictionary.value module /#resolver)
         {.#Some [id {.#None}]}
         {try.#Success (|> archive
                           representation
@@ -143,7 +143,7 @@
   (def .public (find module archive)
     (-> descriptor.Module Archive (Try (Entry Any)))
     (let [(open "/[0]") (representation archive)]
-      (case (dictionary.value module /#resolver)
+      (when (dictionary.value module /#resolver)
         {.#Some [id {.#Some entry}]}
         {try.#Success entry}
 
@@ -155,7 +155,7 @@
 
   (def .public (archived? archive module)
     (-> Archive descriptor.Module Bit)
-    (case (..find module archive)
+    (when (..find module archive)
       {try.#Success _}
       true
 
@@ -168,14 +168,14 @@
          (the #resolver)
          dictionary.entries
          (list.all (function (_ [module [id descriptor+document]])
-                     (case descriptor+document
+                     (when descriptor+document
                        {.#Some _} {.#Some module}
                        {.#None} {.#None})))))
 
   (def .public (reserved? archive module)
     (-> Archive descriptor.Module Bit)
     (let [(open "/[0]") (representation archive)]
-      (case (dictionary.value module /#resolver)
+      (when (dictionary.value module /#resolver)
         {.#Some [id _]}
         true
 
@@ -204,7 +204,7 @@
           (revised #next (n.max +next))
           (revised #resolver (function (_ resolver)
                                (list#mix (function (_ [module [id entry]] resolver)
-                                           (case entry
+                                           (when entry
                                              {.#Some _}
                                              (dictionary.has module [id entry] resolver)
                                              
@@ -240,7 +240,7 @@
       (|> /#resolver
           dictionary.entries
           (list.all (function (_ [module [id descriptor+document]])
-                      (case descriptor+document
+                      (when descriptor+document
                         {.#Some _} {.#Some [module id]}
                         {.#None} {.#None})))
           [version /#next]
diff --git a/stdlib/source/library/lux/meta/compiler/meta/archive/artifact/category.lux b/stdlib/source/library/lux/meta/compiler/meta/archive/artifact/category.lux
index 706ea16ae..0afb9adc5 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/archive/artifact/category.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/archive/artifact/category.lux
@@ -45,7 +45,7 @@
   (Equivalence Category)
   (implementation
    (def (= left right)
-     (case [left right]
+     (when [left right]
        [{#Anonymous} {#Anonymous}]
        true
 
diff --git a/stdlib/source/library/lux/meta/compiler/meta/archive/module/descriptor.lux b/stdlib/source/library/lux/meta/compiler/meta/archive/module/descriptor.lux
index 057f72e6e..f9cfae82a 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/archive/module/descriptor.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/archive/module/descriptor.lux
@@ -41,7 +41,7 @@
   (Equivalence Module_State)
   (implementation
    (def (= left right)
-     (case [left right]
+     (when [left right]
        (^.with_template [<tag>]
          [[{<tag>} {<tag>}]
           true])
diff --git a/stdlib/source/library/lux/meta/compiler/meta/archive/registry.lux b/stdlib/source/library/lux/meta/compiler/meta/archive/registry.lux
index 48f9fb04c..9f1e240d9 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/archive/registry.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/archive/registry.lux
@@ -82,7 +82,7 @@
            sequence.list
            (list.all (|>> product.left
                           (the //.#category)
-                          (pipe.case
+                          (pipe.when
                             {<tag> it} {.#Some it}
                             _ {.#None})))))]
 
@@ -119,7 +119,7 @@
                               ))
           category (is (Format Category)
                        (function (_ value)
-                         (case value
+                         (when value
                            (^.with_template [<nat> <tag> <format>]
                              [{<tag> value}
                               ((binary.and binary.nat <format>) [<nat> value])])
@@ -164,7 +164,7 @@
           category (is (Parser Category)
                        (do [! <>.monad]
                          [tag <binary>.nat]
-                         (case tag
+                         (when tag
                            (^.with_template [<nat> <tag> <parser>]
                              [<nat>
                               (at ! each (|>> {<tag>}) <parser>)])
@@ -185,7 +185,7 @@
       (|> (<binary>.sequence_64 (all <>.and category mandatory? dependencies))
           (at <>.monad each (sequence#mix (function (_ [category mandatory? dependencies] registry)
                                             (product.right
-                                             (case category
+                                             (when category
                                                {//category.#Anonymous}
                                                (..resource mandatory? dependencies registry)
 
diff --git a/stdlib/source/library/lux/meta/compiler/meta/cache/dependency/artifact.lux b/stdlib/source/library/lux/meta/compiler/meta/cache/dependency/artifact.lux
index 9f1d8bf22..26f28d451 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/cache/dependency/artifact.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/cache/dependency/artifact.lux
@@ -38,7 +38,7 @@
   (-> (-> Synthesis (List Constant))
       (-> Path (List Constant)))
   (function (again path)
-    (case path
+    (when path
       (^.or {synthesis.#Pop}
             {synthesis.#Access _}
             {synthesis.#Bind _})
@@ -52,8 +52,8 @@
       ([synthesis.#Alt]
        [synthesis.#Seq])
       
-      {synthesis.#Bit_Fork when then else}
-      (case else
+      {synthesis.#Bit_Fork test then else}
+      (when else
         {.#Some else}
         (.all list#composite
               (again then)
@@ -76,12 +76,12 @@
 
 (def (references value)
   (-> Synthesis (List Constant))
-  (case value
+  (when value
     {synthesis.#Simple value}
     (list)
     
     {synthesis.#Structure value}
-    (case value
+    (when value
       {analysis/complex.#Variant value}
       (|> value
           (the analysis/complex.#value)
@@ -93,7 +93,7 @@
           list#conjoint))
 
     {synthesis.#Reference value}
-    (case value
+    (when value
       {reference.#Variable _}
       (list)
       
@@ -101,9 +101,9 @@
       (list value))
     
     {synthesis.#Control value}
-    (case value
+    (when value
       {synthesis.#Branch value}
-      (case value
+      (when value
         {synthesis.#Exec this that}
         (.all list#composite
               (references this)
@@ -123,13 +123,13 @@
         {synthesis.#Get _ record}
         (references record)
         
-        {synthesis.#Case input path}
+        {synthesis.#When input path}
         (.all list#composite
               (references input)
               (path_references references path)))
       
       {synthesis.#Loop value}
-      (case value
+      (when value
         {synthesis.#Scope value}
         (let [of_inits (|> value
                            (the synthesis.#inits)
@@ -145,7 +145,7 @@
             list#conjoint))
       
       {synthesis.#Function value}
-      (case value
+      (when value
         {synthesis.#Abstraction value}
         (|> value
             (the synthesis.#body)
@@ -217,11 +217,11 @@
   (let [[mandatory immediate] (immediate_dependencies archive)]
     (loop (again [pending mandatory
                   minimum unit.none])
-      (case pending
+      (when pending
         {.#Item head tail}
         (if (set.member? minimum head)
           (again tail minimum)
-          (again (case (dictionary.value head immediate)
+          (again (when (dictionary.value head immediate)
                    {.#Some additional}
                    (list#composite (set.list additional) tail)
 
diff --git a/stdlib/source/library/lux/meta/compiler/meta/cache/dependency/module.lux b/stdlib/source/library/lux/meta/compiler/meta/cache/dependency/module.lux
index 0a9b6028f..60e4af536 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/cache/dependency/module.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/cache/dependency/module.lux
@@ -57,7 +57,7 @@
   (let [memo (is (Memo descriptor.Module Ancestry)
                  (function (_ again module)
                    (do [! state.monad]
-                     [.let [parents (case (archive.find module archive)
+                     [.let [parents (when (archive.find module archive)
                                       {try.#Success [module output registry]}
                                       (the [module.#descriptor descriptor.#references] module)
                                       
diff --git a/stdlib/source/library/lux/meta/compiler/meta/cache/module.lux b/stdlib/source/library/lux/meta/compiler/meta/cache/module.lux
index 081911993..619e3db90 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/cache/module.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/cache/module.lux
@@ -55,14 +55,14 @@
                                                                      error])]
         (do !
           [? (//.enable! ! fs context)]
-          (case ?
+          (when ?
             {try.#Failure error}
             (in <failure>)
             
             success
             (|> path
                 (at fs make_directory)
-                (at ! each (|>> (pipe.case
+                (at ! each (|>> (pipe.when
                                   {try.#Failure error}
                                   <failure>
 
diff --git a/stdlib/source/library/lux/meta/compiler/meta/cli.lux b/stdlib/source/library/lux/meta/compiler/meta/cli.lux
index 21d0885ad..37adb69f4 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/cli.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/cli.lux
@@ -114,7 +114,7 @@
 
 (def .public target
   (-> Service Target)
-  (|>> (pipe.case
+  (|>> (pipe.when
          (^.or {#Compilation [host_dependencies libraries compilers sources target module]}
                {#Interpretation [host_dependencies libraries compilers sources target module]}
                {#Export [sources target]})
diff --git a/stdlib/source/library/lux/meta/compiler/meta/import.lux b/stdlib/source/library/lux/meta/compiler/meta/import.lux
index b904d3df6..500de0a6f 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/import.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/import.lux
@@ -50,10 +50,10 @@
                           (at ! conjoint)
                           (at ! each (|>> sequence.list
                                           (monad.mix ! (function (_ entry import)
-                                                         (case entry
+                                                         (when entry
                                                            {tar.#Normal [path instant mode ownership content]}
                                                            (let [path (tar.from_path path)]
-                                                             (case (dictionary.has' path (tar.data content) import)
+                                                             (when (dictionary.has' path (tar.data content) import)
                                                                {try.#Failure error}
                                                                (exception.except ..duplicate [library path])
 
diff --git a/stdlib/source/library/lux/meta/compiler/meta/io/archive.lux b/stdlib/source/library/lux/meta/compiler/meta/io/archive.lux
index cf8d212f8..40e32ad80 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/io/archive.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/io/archive.lux
@@ -120,13 +120,13 @@
                                              bundles ..empty_bundles
                                              output (is Output sequence.empty)])
                                  (let [[analysers synthesizers generators declarations] bundles]
-                                   (case input
+                                   (when input
                                      {.#Item [[[@artifact artifact_category mandatory_artifact?] artifact_dependencies] input']}
-                                     (case (do !
+                                     (when (do !
                                              [data (try.of_maybe (dictionary.value (format (%.nat @artifact) extension) actual))
                                               .let [context [@module @artifact]
                                                     declaration (at host ingest context data)]]
-                                             (case artifact_category
+                                             (when artifact_category
                                                {category.#Anonymous}
                                                (do !
                                                  [.let [output (sequence.suffix [@artifact {.#None} data] output)]
@@ -220,7 +220,7 @@
                                      {try.#Success [definitions bundles output]}))))
      content (document.content $.key document)
      definitions (monad.each ! (function (_ [def_name def_global])
-                                 (case def_global
+                                 (when def_global
                                    (^.with_template [<tag>]
                                      [{<tag> payload}
                                       (in [def_name {<tag> payload}])])
@@ -269,7 +269,7 @@
 
 (def (cache_parser customs)
   (-> (List Custom) (Parser [(module.Module Any) Registry]))
-  (case (for @.old (as (List (Custom Any Any Any))
+  (when (for @.old (as (List (Custom Any Any Any))
                        customs)
              customs)
     {.#End}
@@ -380,7 +380,7 @@
         (Async (Try [Archive .Lux Bundles]))))
   (do async.monad
     [binary (at fs read (cache/archive.descriptor fs context))]
-    (case binary
+    (when binary
       {try.#Success binary}
       (do (try.with async.monad)
         [archive (async#in (archive.import ///.version binary))]
diff --git a/stdlib/source/library/lux/meta/compiler/meta/io/context.lux b/stdlib/source/library/lux/meta/compiler/meta/io/context.lux
index d5cc32d72..e6a80f7a5 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/io/context.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/io/context.lux
@@ -58,7 +58,7 @@
 (def (find_source_file fs importer contexts module extension)
   (-> (file.System Async) Module (List Context) Module Extension
       (Async (Try file.Path)))
-  (case contexts
+  (when contexts
     {.#End}
     (async#in (exception.except ..cannot_find_module [importer module]))
 
@@ -81,7 +81,7 @@
   ... Normal Lux files (i.e. without a host extension) are then picked as fallback files.
   (do [! async.monad]
     [outcome (..find_source_file fs importer contexts module (..full_host_extension partial_host_extension))]
-    (case outcome
+    (when outcome
       {try.#Success path}
       (|> path
           (at fs read)
@@ -97,13 +97,13 @@
 (def (find_library_source_file importer import partial_host_extension module)
   (-> Module Import Extension Module (Try [file.Path Binary]))
   (let [path (format module (..full_host_extension partial_host_extension))]
-    (case (dictionary.value path import)
+    (when (dictionary.value path import)
       {.#Some data}
       {try.#Success [path data]}
 
       {.#None}
       (let [path (format module ..lux_extension)]
-        (case (dictionary.value path import)
+        (when (dictionary.value path import)
           {.#Some data}
           {try.#Success [path data]}
 
@@ -117,7 +117,7 @@
   ... Normal Lux files (i.e. without a host extension) are then picked as fallback files.
   (do [! async.monad]
     [outcome (find_local_source_file fs importer import contexts partial_host_extension module)]
-    (case outcome
+    (when outcome
       {try.#Success [path data]}
       (in outcome)
 
@@ -129,7 +129,7 @@
       (Async (Try Input)))
   (do (try.with async.monad)
     [[path binary] (..find_any_source_file fs importer import contexts partial_host_extension module)]
-    (case (at utf8.codec decoded binary)
+    (when (at utf8.codec decoded binary)
       {try.#Success code}
       (in [////.#module module
            ////.#file path
diff --git a/stdlib/source/library/lux/meta/compiler/meta/packager/jvm.lux b/stdlib/source/library/lux/meta/compiler/meta/packager/jvm.lux
index b783f1262..1fbba7497 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/packager/jvm.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/packager/jvm.lux
@@ -140,7 +140,7 @@
                   (java/util/jar/Attributes::put (java/util/jar/Attributes$Name::MANIFEST_VERSION)
                                                  (ffi.as_string ..manifest_version)))]
     (exec
-      (case program
+      (when program
         {.#Some program}
         (to attrs
             (java/util/jar/Attributes::put (java/util/jar/Attributes$Name::MAIN_CLASS)
@@ -188,7 +188,7 @@
         chunk_size (.int ..mebi_byte)
         buffer (java/io/ByteArrayOutputStream::new (ffi.as_int chunk_size))]
     (loop (again [so_far 0])
-      (case (ffi.of_int (java/io/InputStream::read chunk (ffi.as_int +0) (ffi.as_int chunk_size) input))
+      (when (ffi.of_int (java/io/InputStream::read chunk (ffi.as_int +0) (ffi.as_int chunk_size) input))
         -1
         [so_far
          (java/io/ByteArrayOutputStream::toByteArray buffer)]
@@ -213,7 +213,7 @@
 
 (def (read_jar_entry entry input)
   (-> java/util/jar/JarEntry java/util/jar/JarInputStream [Nat Binary])
-  (case (ffi.of_long (java/util/zip/ZipEntry::getSize entry))
+  (when (ffi.of_long (java/util/zip/ZipEntry::getSize entry))
     -1
     (..read_jar_entry_with_unknown_size input)
     
@@ -230,12 +230,12 @@
     (loop (again [entries entries
                   duplicates duplicates
                   sink sink])
-      (case (java/util/jar/JarInputStream::getNextJarEntry input)
+      (when (java/util/jar/JarInputStream::getNextJarEntry input)
         {try.#Failure error}
         {try.#Failure error}
         
         {try.#Success ?entry}
-        (case ?entry
+        (when ?entry
           {.#None}
           (exec
             (java/io/Closeable::close input)
@@ -249,7 +249,7 @@
                              (text.starts_with? "META-INF/leiningen/" entry_path))
                          (or (text.ends_with? ".SF" entry_path)
                              (text.ends_with? ".DSA" entry_path))))
-              (case (java/util/jar/JarOutputStream::putNextEntry (java/util/jar/JarEntry::new (ffi.as_string entry_path))
+              (when (java/util/jar/JarOutputStream::putNextEntry (java/util/jar/JarEntry::new (ffi.as_string entry_path))
                                                                  sink)
                 {try.#Failure error}
                 (again entries
diff --git a/stdlib/source/library/lux/meta/compiler/meta/packager/ruby.lux b/stdlib/source/library/lux/meta/compiler/meta/packager/ruby.lux
index 1c0d70dc2..80be5feaf 100644
--- a/stdlib/source/library/lux/meta/compiler/meta/packager/ruby.lux
+++ b/stdlib/source/library/lux/meta/compiler/meta/packager/ruby.lux
@@ -49,7 +49,7 @@
   (-> descriptor.Module module.ID (Set unit.ID) Output (Try (Maybe _.Statement)))
   (do [! try.monad]
     []
-    (case (|> output
+    (when (|> output
               sequence.list
               (list.only (function (_ [artifact_id custom content])
                            (set.member? necessary_dependencies [module_id artifact_id]))))
@@ -86,7 +86,7 @@
   (do [! try.monad]
     [bundle (is (Try (Maybe _.Statement))
                 (..bundle_module module module_id necessary_dependencies (the archive.#output entry)))]
-    (case bundle
+    (when bundle
       {.#None}
       (in sink)
 
diff --git a/stdlib/source/library/lux/meta/compiler/phase.lux b/stdlib/source/library/lux/meta/compiler/phase.lux
index 2b67baec4..b5d04c40e 100644
--- a/stdlib/source/library/lux/meta/compiler/phase.lux
+++ b/stdlib/source/library/lux/meta/compiler/phase.lux
@@ -29,7 +29,7 @@
   (implementation
    (def (each f it)
      (function (_ state)
-       (case (it state)
+       (when (it state)
          {try.#Success [state' output]}
          {try.#Success [state' (f output)]}
          
@@ -47,7 +47,7 @@
 
    (def (conjoint it)
      (function (_ state)
-       (case (it state)
+       (when (it state)
          {try.#Success [state' it']}
          (it' state')
          
diff --git a/stdlib/source/library/lux/meta/compiler/reference.lux b/stdlib/source/library/lux/meta/compiler/reference.lux
index 340cf1a0d..b7eb370de 100644
--- a/stdlib/source/library/lux/meta/compiler/reference.lux
+++ b/stdlib/source/library/lux/meta/compiler/reference.lux
@@ -31,7 +31,7 @@
   (Equivalence Reference)
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        (^.with_template [<tag> <equivalence>]
          [[{<tag> reference} {<tag> sample}]
           (at <equivalence> = reference sample)])
@@ -48,7 +48,7 @@
      ..equivalence)
 
    (def (hash value)
-     (case value
+     (when value
        (^.with_template [<factor> <tag> <hash>]
          [{<tag> value}
           (|> value
@@ -85,7 +85,7 @@
 
 (def .public format
   (Format Reference)
-  (|>> (pipe.case
+  (|>> (pipe.when
          {#Variable variable}
          (/variable.format variable)
          
diff --git a/stdlib/source/library/lux/meta/compiler/reference/variable.lux b/stdlib/source/library/lux/meta/compiler/reference/variable.lux
index caa6d2c89..0e038ed06 100644
--- a/stdlib/source/library/lux/meta/compiler/reference/variable.lux
+++ b/stdlib/source/library/lux/meta/compiler/reference/variable.lux
@@ -29,7 +29,7 @@
   (Equivalence Variable)
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        (^.with_template [<tag>]
          [[{<tag> reference'} {<tag> sample'}]
           (n.= reference' sample')])
@@ -45,7 +45,7 @@
      ..equivalence)
    
    (def hash
-     (|>> (pipe.case
+     (|>> (pipe.when
             (^.with_template [<factor> <tag>]
               [{<tag> register}
                (|> register
@@ -60,7 +60,7 @@
 
 (def .public self?
   (-> Variable Bit)
-  (|>> (pipe.case
+  (|>> (pipe.when
          (..self)
          true
 
@@ -69,7 +69,7 @@
 
 (def .public format
   (Format Variable)
-  (|>> (pipe.case
+  (|>> (pipe.when
          {#Local local}
          (%.format "+" (%.nat local))
          
diff --git a/stdlib/source/library/lux/meta/configuration.lux b/stdlib/source/library/lux/meta/configuration.lux
index 45ca34758..b98d92ee1 100644
--- a/stdlib/source/library/lux/meta/configuration.lux
+++ b/stdlib/source/library/lux/meta/configuration.lux
@@ -74,7 +74,7 @@
 
 (def (subsumes? actual expected)
   (-> Configuration Configuration Bit)
-  (case expected
+  (when expected
     {.#End}
     true
 
@@ -90,7 +90,7 @@
               default (<>.maybe <code>.any)])
     (do meta.monad
       [actual meta.configuration]
-      (case (list#mix (function (_ [expected then] choice)
+      (when (list#mix (function (_ [expected then] choice)
                         (if (subsumes? actual expected)
                           {.#Some then}
                           choice))
diff --git a/stdlib/source/library/lux/meta/extension.lux b/stdlib/source/library/lux/meta/extension.lux
index f4e7b41d7..175b1143f 100644
--- a/stdlib/source/library/lux/meta/extension.lux
+++ b/stdlib/source/library/lux/meta/extension.lux
@@ -50,7 +50,7 @@
          (with_symbols [g!handler g!inputs g!error g!_]
            (in (list (` (<extension> (, name)
                                      (.function ((, g!handler) (, g!name) (, g!phase) (, g!archive) (, g!inputs))
-                                       (.case (<result>
+                                       (.when (<result>
                                                (monad.do <>.monad
                                                  [(,* inputs)
                                                   (, g!_) <end>]
diff --git a/stdlib/source/library/lux/meta/location.lux b/stdlib/source/library/lux/meta/location.lux
index a9e62dd5f..2c4fc0eb1 100644
--- a/stdlib/source/library/lux/meta/location.lux
+++ b/stdlib/source/library/lux/meta/location.lux
@@ -20,7 +20,7 @@
 
 (def .public here
   (macro (_ tokens compiler)
-    (case tokens
+    (when tokens
       {.#End}
       (let [location (the .#location compiler)]
         {.#Right [compiler
diff --git a/stdlib/source/library/lux/meta/macro.lux b/stdlib/source/library/lux/meta/macro.lux
index 0b7bb514a..298bde13d 100644
--- a/stdlib/source/library/lux/meta/macro.lux
+++ b/stdlib/source/library/lux/meta/macro.lux
@@ -27,7 +27,7 @@
 
 (def (local ast)
   (-> Code (Meta Text))
-  (case ast
+  (when ast
     [_ {.#Symbol ["" name]}]
     (at //.monad in name)
 
@@ -42,7 +42,7 @@
 
 (def .public with_symbols
   (.macro (_ tokens)
-    (case tokens
+    (when tokens
       (list [_ {.#Tuple symbols}] body)
       (do [! //.monad]
         [symbol_names (monad.each ! ..local symbols)
@@ -58,11 +58,11 @@
 
 (def .public times
   (.macro (_ tokens)
-    (case tokens
+    (when tokens
       (list.partial [_ {.#Nat times}] terms)
       (loop (again [times times
                     before terms])
-        (case times
+        (when times
           0
           (at //.monad in before)
 
diff --git a/stdlib/source/library/lux/meta/macro/context.lux b/stdlib/source/library/lux/meta/macro/context.lux
index 73cda9cd0..5a347775d 100644
--- a/stdlib/source/library/lux/meta/macro/context.lux
+++ b/stdlib/source/library/lux/meta/macro/context.lux
@@ -33,7 +33,7 @@
   (do meta.monad
     [.let [[@ expected_name] it]
      defs (meta.definitions @)]
-    (case (list.one (function (_ [actual_name [exported? type value]])
+    (when (list.one (function (_ [actual_name [exported? type value]])
                       (if (text#= expected_name actual_name)
                         {.#Some value}
                         {.#None}))
@@ -50,7 +50,7 @@
   (All (_ a) (-> (Stack a) Symbol (Meta a)))
   (do meta.monad
     [stack (..global context)]
-    (case (|> stack
+    (when (|> stack
               (as (Stack Any))
               list.head)
       {.#Some top}
@@ -69,7 +69,7 @@
   (All (_ a) (-> (Stack a) (Predicate a) Symbol (Meta a)))
   (do meta.monad
     [stack (..global context)]
-    (case (|> stack
+    (when (|> stack
               (as (Stack Any))
               (list.example (as (Predicate Any) ?)))
       {.#Some it}
@@ -88,7 +88,7 @@
   (function (_ lux)
     (let [on_global (is (-> Global Global)
                         (function (_ it)
-                          (case it
+                          (when it
                             {.#Definition it}
                             {.#Definition (on_definition it)}
                             
diff --git a/stdlib/source/library/lux/meta/macro/expansion.lux b/stdlib/source/library/lux/meta/macro/expansion.lux
index eb30d4ee8..9364ecc77 100644
--- a/stdlib/source/library/lux/meta/macro/expansion.lux
+++ b/stdlib/source/library/lux/meta/macro/expansion.lux
@@ -20,11 +20,11 @@
 
 (def .public (single syntax)
   (-> Code (Meta (List Code)))
-  (case syntax
+  (when syntax
     [_ {.#Form {.#Item [[_ {.#Symbol name}] args]}}]
     (do ///.monad
       [?macro (///.macro name)]
-      (case ?macro
+      (when ?macro
         {.#Some macro}
         ((as Macro' macro) args)
         
@@ -36,11 +36,11 @@
 
 (def .public (complete syntax)
   (-> Code (Meta (List Code)))
-  (case syntax
+  (when syntax
     [_ {.#Form {.#Item [[_ {.#Symbol name}] args]}}]
     (do ///.monad
       [?macro (///.macro name)]
-      (case ?macro
+      (when ?macro
         {.#Some macro}
         (do [! ///.monad]
           [top_level_complete ((as Macro' macro) args)]
@@ -56,11 +56,11 @@
 
 (def .public (total syntax)
   (-> Code (Meta (List Code)))
-  (case syntax
+  (when syntax
     [_ {.#Form {.#Item [[_ {.#Symbol name}] args]}}]
     (do ///.monad
       [?macro (///.macro name)]
-      (case ?macro
+      (when ?macro
         {.#Some macro}
         (do ///.monad
           [complete ((as Macro' macro) args)
@@ -95,7 +95,7 @@
   (-> Code (Meta Code))
   (do ///.monad
     [token+ (..complete token)]
-    (case token+
+    (when token+
       (list token')
       (in token')
 
@@ -108,8 +108,8 @@
        (let [[module _] (.symbol .._)
              [_ short] (.symbol <macro>)
              macro_name [module short]]
-         (case (is (Maybe [Bit Code])
-                   (case tokens
+         (when (is (Maybe [Bit Code])
+                   (when tokens
                      (list [_ {.#Text "omit"}]
                            token)
                      {.#Some [true token]}
diff --git a/stdlib/source/library/lux/meta/macro/local.lux b/stdlib/source/library/lux/meta/macro/local.lux
index 8e0d8d709..c69b32f95 100644
--- a/stdlib/source/library/lux/meta/macro/local.lux
+++ b/stdlib/source/library/lux/meta/macro/local.lux
@@ -37,9 +37,9 @@
 (def (with_module name body)
   (All (_ a) (-> Text (-> Module (Try [Module a])) (Meta a)))
   (function (_ compiler)
-    (case (|> compiler (the .#modules) (property.value name))
+    (when (|> compiler (the .#modules) (property.value name))
       {.#Some module}
-      (case (body module)
+      (when (body module)
         {try.#Success [module' output]}
         {try.#Success [(revised .#modules (property.has name module') compiler)
                        output]}
@@ -59,7 +59,7 @@
                           (property.has definition_name definition))]]
     (..with_module module_name
       (function (_ module)
-        (case (|> module (the .#definitions) (property.value definition_name))
+        (when (|> module (the .#definitions) (property.value definition_name))
           {.#None}
           {try.#Success [(revised .#definitions add_macro! module)
                          []]}
@@ -75,7 +75,7 @@
                             (property.lacks definition_name))]]
     (..with_module module_name
       (function (_ module)
-        (case (|> module (the .#definitions) (property.value definition_name))
+        (when (|> module (the .#definitions) (property.value definition_name))
           {.#Some _}
           {try.#Success [(revised .#definitions lacks_macro! module)
                          []]}
@@ -91,7 +91,7 @@
        [_ (monad.each ! ..pop_one macros)
         _ (..pop_one self)
         compiler meta.compiler_state]
-       (in (case (the .#expected compiler)
+       (in (when (the .#expected compiler)
              {.#Some _}
              (list (' []))
              
@@ -135,7 +135,7 @@
                           locals)
        expression? (is (Meta Bit)
                        (function (_ lux)
-                         {try.#Success [lux (case (the .#expected lux)
+                         {try.#Success [lux (when (the .#expected lux)
                                               {.#None}
                                               false
 
diff --git a/stdlib/source/library/lux/meta/macro/pattern.lux b/stdlib/source/library/lux/meta/macro/pattern.lux
index b639259ba..f4f352efc 100644
--- a/stdlib/source/library/lux/meta/macro/pattern.lux
+++ b/stdlib/source/library/lux/meta/macro/pattern.lux
@@ -19,7 +19,7 @@
 (def locally
   (macro (_ tokens lux)
     (.let [[prelude _] (symbol ._)]
-      (case tokens
+      (when tokens
         (list [@ {.#Symbol ["" name]}])
         {.#Right [lux (list (.` ("lux in-module" (., [@ {.#Text prelude}])
                                  (., [@ {.#Symbol [prelude name]}]))))]}
@@ -68,9 +68,9 @@
 (def .public or
   (pattern
    (macro (_ tokens)
-     (case tokens
+     (when tokens
        (list.partial [_ {.#Form patterns}] body branches)
-       (case patterns
+       (when patterns
          {.#End}
          (///.failure (..wrong_syntax_error (symbol ..or)))
 
@@ -85,12 +85,12 @@
 (def .public with_template
   (pattern
    (macro (_ tokens)
-     (case tokens
+     (when tokens
        (list.partial [_ {.#Form (list [_ {.#Tuple bindings}]
                                       [_ {.#Tuple templates}])}]
                      [_ {.#Form data}]
                      branches)
-       (case (is (Maybe (List Code))
+       (when (is (Maybe (List Code))
                  (do maybe.monad
                    [bindings' (monad.each maybe.monad symbol_short bindings)
                     data' (monad.each maybe.monad tuple_list data)]
@@ -118,7 +118,7 @@
 
 (def (level it)
   (-> Code (Meta Level))
-  (///#in (case it
+  (///#in (when it
             [_ {.#Tuple (list expr binding)}]
             [expr binding]
 
@@ -130,7 +130,7 @@
 
 (def (multiP levels)
   (-> (List Code) (Meta Multi))
-  (case levels
+  (when levels
     {.#End}
     (///.failure "Multi-level patterns cannot be empty.")
 
@@ -142,13 +142,13 @@
 (def (multiG g!_ [[init_pattern levels] body])
   (-> Code [Multi Code] (List Code))
   (.let [inner_pattern_body (list#mix (function (_ [calculation pattern] success)
-                                        (.let [bind? (case pattern
+                                        (.let [bind? (when pattern
                                                        [_ {.#Symbol _}]
                                                        true
 
                                                        _
                                                        false)]
-                                          (.` (case (., calculation)
+                                          (.` (when (., calculation)
                                                 (., pattern)
                                                 (., success)
 
@@ -162,12 +162,12 @@
 (def .public multi
   (pattern
    (macro (_ tokens)
-     (case tokens
+     (when tokens
        (list.partial [_meta {.#Form levels}] body next_branches)
        (with_symbols [g!temp]
          (do ///.monad
            [mlc (multiP levels)
-            .let [initial_bind? (case mlc
+            .let [initial_bind? (when mlc
                                   [[_ {.#Symbol _}] _]
                                   true
 
@@ -179,10 +179,10 @@
                            (., g!temp)
 
                            {.#None}
-                           (.case (., g!temp)
+                           (.when (., g!temp)
                              (.,* next_branches))}
                           ("lux type check" {.#Apply (., (type_code expected)) Maybe}
-                           (.case (., g!temp)
+                           (.when (., g!temp)
                              (.,* (multiG g!temp [mlc body]))
 
                              (.,* (if initial_bind?
@@ -195,11 +195,11 @@
 (def .public let
   (pattern
    (macro (_ tokens)
-     (case tokens
+     (when tokens
        (list.partial [_meta {.#Form (list [_ {.#Symbol ["" name]}] pattern)}] body branches)
        (.let [g!whole (local$ name)]
          (///#in (list.partial g!whole
-                               (.` (case (., g!whole) (., pattern) (., body)))
+                               (.` (when (., g!whole) (., pattern) (., body)))
                                branches)))
        
        _
@@ -208,7 +208,7 @@
 (def .public |>
   (pattern
    (macro (_ tokens)
-     (case tokens
+     (when tokens
        (list.partial [_meta {.#Form (list [_ {.#Symbol ["" name]}] [_ {.#Tuple steps}])}] body branches)
        (.let [g!name (local$ name)]
          (///#in (list.partial g!name
@@ -225,7 +225,7 @@
 
 (def (untemplated_partial_list last inits)
   (-> Code (List Code) Code)
-  (case inits
+  (when inits
     {.#End}
     last
 
@@ -244,12 +244,12 @@
   (with_expansions [<default> (do ///.monad
                                 [=elems (monad.each ///.monad untemplated_pattern elems)]
                                 (in (.` [(., g!meta) {(., <tag>) (., (untemplated_list =elems))}])))]
-    (case (list.reversed elems)
+    (when (list.reversed elems)
       {.#Item [_ {.#Form {.#Item [_ {.#Symbol global}] parameters}}]
               inits}
       (do ///.monad
         [micro (///.try (..named_spliced_unquote global))]
-        (case micro
+        (when micro
           {try.#Success micro}
           (do ///.monad
             [output (..one_expansion ((//.function micro) parameters))
@@ -281,7 +281,7 @@
 (def (untemplated_pattern pattern)
   (-> Code (Meta Code))
   (with_symbols [g!meta]
-    (case pattern
+    (when pattern
       (..with_template [<tag> <gen>]
         [[_ {<tag> value}]
          (///#in (.` [(., g!meta) {<tag> (., (<gen> value))}]))])
@@ -296,7 +296,7 @@
       [@composite {.#Form {.#Item [@global {.#Symbol global}] parameters}}]
       (do [! ///.monad]
         [micro (///.try (..named_unquote global))]
-        (case micro
+        (when micro
           {try.#Success micro}
           (do !
             [[_ output] (..one_expansion ((//.function micro) parameters))]
@@ -316,7 +316,7 @@
 (def .public `
   (pattern
    (macro (_ tokens)
-     (case tokens
+     (when tokens
        (list.partial [_meta {.#Form (list template)}] body branches)
        (do ///.monad
          [pattern (untemplated_pattern template)]
diff --git a/stdlib/source/library/lux/meta/macro/syntax.lux b/stdlib/source/library/lux/meta/macro/syntax.lux
index aa415eeb8..ec96b9e42 100644
--- a/stdlib/source/library/lux/meta/macro/syntax.lux
+++ b/stdlib/source/library/lux/meta/macro/syntax.lux
@@ -18,7 +18,7 @@
 (def .public (self_documenting binding parser)
   (All (_ a) (-> Code (Parser a) (Parser a)))
   (function (_ tokens)
-    (case (parser tokens)
+    (when (parser tokens)
       {try.#Failure error}
       {try.#Failure (all text#composite
                          "Failed to parse: " (code.format binding) text.new_line
@@ -29,7 +29,7 @@
 
 (def (un_paired pairs)
   (All (_ a) (-> (List [a a]) (List a)))
-  (case pairs
+  (when pairs
     {.#Item [x y] pairs'}
     (list.partial x y (un_paired pairs'))
 
@@ -47,11 +47,11 @@
 
 (def .public syntax
   (macro (_ tokens)
-    (case (</>.result ..syntaxP tokens)
+    (when (</>.result ..syntaxP tokens)
       {try.#Success [[name g!state args] body]}
       (with_symbols [g!tokens g!body g!error]
         (do [! meta.monad]
-          [vars+parsers (case (list.pairs args)
+          [vars+parsers (when (list.pairs args)
                           {.#Some args}
                           (monad.each !
                                       (is (-> [Code Code] (Meta [Code Code]))
@@ -59,7 +59,7 @@
                                             (with_expansions [<default> (in [var
                                                                              (` (..self_documenting (' (, var))
                                                                                                     (, parser)))])]
-                                              (case var
+                                              (when var
                                                 [_ {.#Symbol ["" _]}]
                                                 <default>
 
@@ -72,7 +72,7 @@
 
                           _
                           (meta.failure "Syntax pattern expects pairs of bindings and code-parsers."))
-           g!state (case g!state
+           g!state (when g!state
                      {.#Some g!state}
                      (in (code.local g!state))
 
@@ -81,7 +81,7 @@
            this_module meta.current_module_name
            .let [g!name (code.symbol ["" name])]]
           (in (list (` (.macro ((, g!name) (, g!tokens) (, g!state))
-                         (.case (</>.result
+                         (.when (</>.result
                                  (is (</>.Parser (Meta (List Code)))
                                      (do <>.monad
                                        [(,* (..un_paired vars+parsers))]
diff --git a/stdlib/source/library/lux/meta/macro/syntax/declaration.lux b/stdlib/source/library/lux/meta/macro/syntax/declaration.lux
index 1f4a9cccd..511f10c30 100644
--- a/stdlib/source/library/lux/meta/macro/syntax/declaration.lux
+++ b/stdlib/source/library/lux/meta/macro/syntax/declaration.lux
@@ -36,7 +36,7 @@
 (def .public (format value)
   (-> Declaration Code)
   (let [g!name (code.local (the #name value))]
-    (case (the #arguments value)
+    (when (the #arguments value)
       {.#End}
       g!name
       
diff --git a/stdlib/source/library/lux/meta/macro/syntax/definition.lux b/stdlib/source/library/lux/meta/macro/syntax/definition.lux
index 445068226..0f6be7510 100644
--- a/stdlib/source/library/lux/meta/macro/syntax/definition.lux
+++ b/stdlib/source/library/lux/meta/macro/syntax/definition.lux
@@ -55,7 +55,7 @@
   (-> Definition Code)
   (` ((, (code.text ..extension))
       (, (code.local _#name))
-      (, (case _#value
+      (, (when _#value
            {.#Left check}
            (//check.format check)
 
@@ -89,7 +89,7 @@
   (-> Lux (Parser Definition))
   (do <>.monad
     [definition (..parser compiler)
-     _ (case (the #value definition)
+     _ (when (the #value definition)
          {.#Left _}
          (in [])
 
diff --git a/stdlib/source/library/lux/meta/macro/syntax/export.lux b/stdlib/source/library/lux/meta/macro/syntax/export.lux
index 1bc78cb9f..04e5c730a 100644
--- a/stdlib/source/library/lux/meta/macro/syntax/export.lux
+++ b/stdlib/source/library/lux/meta/macro/syntax/export.lux
@@ -17,7 +17,7 @@
       (Parser Code)
       (do [! <>.monad]
         [candidate <code>.next]
-        (case candidate
+        (when candidate
           [_ {.#Symbol ["" _]}]
           (in default_policy)
 
diff --git a/stdlib/source/library/lux/meta/macro/template.lux b/stdlib/source/library/lux/meta/macro/template.lux
index cb6acd2d5..a045bd235 100644
--- a/stdlib/source/library/lux/meta/macro/template.lux
+++ b/stdlib/source/library/lux/meta/macro/template.lux
@@ -53,7 +53,7 @@
   (do <>.monad
     [[module short] parser]
     (in (if module_side?
-          (case module
+          (when module
             "" short
             _ module)
           short))))
@@ -86,7 +86,7 @@
   [(def .public <name>
      (syntax (_ [name (<>.or (<>.and (..part true) (..part false))
                              (..part false))])
-       (case name
+       (when name
          {.#Left [simple complex]}
          (in (list (<complex> [(text.interposed "" simple)
                                (text.interposed "" complex)])))
@@ -102,9 +102,9 @@
 
 (def (applied env template)
   (-> Environment Code Code)
-  (case template
+  (when template
     [_ {.#Symbol "" name}]
-    (case (dictionary.value name env)
+    (when (dictionary.value name env)
       {.#Some substitute}
       substitute
 
@@ -164,7 +164,7 @@
       [here_name meta.current_module_name
        expression? (is (Meta Bit)
                        (function (_ lux)
-                         {try.#Success [lux (case (the .#expected lux)
+                         {try.#Success [lux (when (the .#expected lux)
                                               {.#None}
                                               false
 
diff --git a/stdlib/source/library/lux/meta/static.lux b/stdlib/source/library/lux/meta/static.lux
index 617ce7cdb..9a8d25cfe 100644
--- a/stdlib/source/library/lux/meta/static.lux
+++ b/stdlib/source/library/lux/meta/static.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except nat int rev if cond)
+  [lux (.except nat int rev if cond when)
    [abstract
     [monad (.only do)]]
    [control
diff --git a/stdlib/source/library/lux/meta/symbol.lux b/stdlib/source/library/lux/meta/symbol.lux
index e46516bb9..edbf2acd3 100644
--- a/stdlib/source/library/lux/meta/symbol.lux
+++ b/stdlib/source/library/lux/meta/symbol.lux
@@ -46,12 +46,12 @@
   (Codec Text Symbol)
   (implementation
    (def (encoded [module short])
-     (case module
+     (when module
        "" short
        _ (all text#composite module ..separator short)))
    
    (def (decoded input)
-     (case (text.all_split_by ..separator input)
+     (when (text.all_split_by ..separator input)
        (list short)
        {.#Right ["" short]}
 
diff --git a/stdlib/source/library/lux/meta/target/common_lisp.lux b/stdlib/source/library/lux/meta/target/common_lisp.lux
index b7ce2a7fb..9d92f4557 100644
--- a/stdlib/source/library/lux/meta/target/common_lisp.lux
+++ b/stdlib/source/library/lux/meta/target/common_lisp.lux
@@ -77,7 +77,7 @@
 
   (def .public bool
     (-> Bit Literal)
-    (|>> (pipe.case
+    (|>> (pipe.when
            #0 ..nil
            #1 (..symbol "t"))))
 
@@ -154,7 +154,7 @@
 
   (def .public (args& singles rest)
     (-> (List Var/1) Var/1 Var/*)
-    (|> (case singles
+    (|> (when singles
           {.#End}
           ""
           
@@ -404,7 +404,7 @@
   (with_template [<name> <prefix>]
     [(def .public (<name> conditions expression)
        (-> (List Text) (Expression Any) (Expression Any))
-       (case conditions
+       (when conditions
          {.#End}
          expression
          
diff --git a/stdlib/source/library/lux/meta/target/js.lux b/stdlib/source/library/lux/meta/target/js.lux
index e5a1ce144..37792d6bc 100644
--- a/stdlib/source/library/lux/meta/target/js.lux
+++ b/stdlib/source/library/lux/meta/target/js.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except Location Code Label or and function if undefined for comment not int try ++ -- the type_of at ,)
+  [lux (.except Location Code Label or and function if undefined for comment not int try ++ -- the type_of at , when)
    [control
     ["[0]" pipe]]
    [data
@@ -73,7 +73,7 @@
 
   (def .public boolean
     (-> Bit Literal)
-    (|>> (pipe.case
+    (|>> (pipe.when
            #0 "false"
            #1 "true")
          abstraction))
@@ -414,7 +414,7 @@
                                                               (..nested (representation then)))))
                                          (text.interposed \n+))
                                      \n+
-                                     (case default
+                                     (.when default
                                        {.#Some default}
                                        (format "default:"
                                                (..nested (representation default)))
diff --git a/stdlib/source/library/lux/meta/target/jvm/attribute.lux b/stdlib/source/library/lux/meta/target/jvm/attribute.lux
index 0b0af146e..c6ff2472f 100644
--- a/stdlib/source/library/lux/meta/target/jvm/attribute.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/attribute.lux
@@ -87,7 +87,7 @@
 
 (def (length attribute)
   (-> Attribute Nat)
-  (case attribute
+  (when attribute
     (^.with_template [<tag>]
       [{<tag> [name length info]}
        (|> length //unsigned.value (n.+ ..common_attribute_length))])
@@ -139,7 +139,7 @@
 
 (def .public (format it)
   (Format Attribute)
-  (case it
+  (when it
     {#Constant it}
     ((info_format /constant.format) it)
     
diff --git a/stdlib/source/library/lux/meta/target/jvm/bytecode.lux b/stdlib/source/library/lux/meta/target/jvm/bytecode.lux
index 6123ee60e..57ea8caf8 100644
--- a/stdlib/source/library/lux/meta/target/jvm/bytecode.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/bytecode.lux
@@ -85,7 +85,7 @@
 
 (def try|do
   (template (_ <binding> <term> <then>)
-    [(.case <term>
+    [(.when <term>
        {try.#Success <binding>}
        <then>
 
@@ -151,7 +151,7 @@
     (let [[pool environment tracker] state]
       {try.#Success [state
                      [..relative#identity
-                      (case (dictionary.value label (the #known tracker))
+                      (when (dictionary.value label (the #known tracker))
                         {.#Some [expected {.#Some address}]}
                         {.#Some [expected address]}
                         
@@ -164,7 +164,7 @@
     (let [[pool environment tracker] state]
       {try.#Success [state
                      [..relative#identity
-                      (case (dictionary.value label (the #known tracker))
+                      (when (dictionary.value label (the #known tracker))
                         {.#Some [expected {.#None}]}
                         {.#Some expected}
 
@@ -190,7 +190,7 @@
     (-> Label (Bytecode Any))
     (function (_ [pool environment tracker])
       (let [@here (the #program_counter tracker)]
-        (case (dictionary.value label (the #known tracker))
+        (when (dictionary.value label (the #known tracker))
           {.#Some [expected {.#Some address}]}
           (exception.except ..label_has_already_been_set [label])
           
@@ -211,7 +211,7 @@
   (implementation
    (def (each $ it)
      (function (_ state)
-       (case (it state)
+       (when (it state)
          {try.#Success [state' [relative it]]}
          {try.#Success [state' [relative ($ it)]]}
          
@@ -230,9 +230,9 @@
 
    (def (conjoint ^^it)
      (function (_ state)
-       (case (^^it state)
+       (when (^^it state)
          {try.#Success [state' [left ^it]]}
-         (case (^it state')
+         (when (^it state')
            {try.#Success [state'' [right it]]}
            {try.#Success [state'' [(relative#composite left right) it]]}
            
@@ -248,7 +248,7 @@
   (-> (Bytecode Any) (Bytecode Any))
   (do ..monad
     [stack ..stack]
-    (.case stack
+    (.when stack
       {.#Some _}
       it
 
@@ -260,7 +260,7 @@
   (-> Label (Bytecode Any) (Bytecode Any))
   (do ..monad
     [?@ (..acknowledged? @)]
-    (.case ?@
+    (.when ?@
       {.#Some _}
       it
 
@@ -557,7 +557,7 @@
   (-> //constant.UTF8 (Bytecode Any))
   (do ..monad
     [index (..lifted (//constant/pool.string value))]
-    (case (|> index //index.value //unsigned.value //unsigned.u1)
+    (when (|> index //index.value //unsigned.value //unsigned.u1)
       {try.#Success index}
       (..bytecode $0 $1 @_ _.ldc [index])
 
@@ -575,14 +575,14 @@
 (with_template [<name> <type> <constructor> <constant> <wide> <to_lux> <specializations>]
   [(def .public (<name> value)
      (-> <type> (Bytecode Any))
-     (case (|> value <to_lux>)
+     (when (|> value <to_lux>)
        (^.with_template [<special> <instruction>]
          [<special> (..bytecode $0 $1 @_ <instruction> [])])
        <specializations>
        
        _ (do ..monad
            [index (..lifted (<constant> (<constructor> value)))]
-           (case (|> index //index.value //unsigned.value //unsigned.u1)
+           (when (|> index //index.value //unsigned.value //unsigned.u1)
              {try.#Success index}
              (..bytecode $0 $1 @_ _.ldc [index])
 
@@ -604,7 +604,7 @@
   (-> java/lang/Float (Bytecode Any))
   (do ..monad
     [index (..lifted (//constant/pool.float (//constant.float value)))]
-    (case (|> index //index.value //unsigned.value //unsigned.u1)
+    (when (|> index //index.value //unsigned.value //unsigned.u1)
       {try.#Success index}
       (..bytecode $0 $1 @_ _.ldc [index])
 
@@ -625,7 +625,7 @@
   (if (i.= ..negative_zero_float_bits
            (..float_bits value))
     (..arbitrary_float value)
-    (case (|> value ffi.float_to_double (as Frac))
+    (when (|> value ffi.float_to_double (as Frac))
       (^.with_template [<special> <instruction>]
         [<special> (..bytecode $0 $1 @_ <instruction> [])])
       ([+0.0 _.fconst_0]
@@ -637,7 +637,7 @@
 (with_template [<name> <type> <constructor> <constant> <wide> <to_lux> <specializations>]
   [(def .public (<name> value)
      (-> <type> (Bytecode Any))
-     (case (|> value <to_lux>)
+     (when (|> value <to_lux>)
        (^.with_template [<special> <instruction>]
          [<special> (..bytecode $0 $2 @_ <instruction> [])])
        <specializations>
@@ -671,7 +671,7 @@
   (if (i.= ..negative_zero_double_bits
            (..double_bits value))
     (..arbitrary_double value)
-    (case (as Frac value)
+    (when (as Frac value)
       (^.with_template [<special> <instruction>]
         [<special> (..bytecode $0 $2 @_ <instruction> [])])
       ([+0.0 _.dconst_0]
@@ -685,7 +685,7 @@
 
 (def (register id)
   (-> Nat (Bytecode Register))
-  (case (//unsigned.u1 id)
+  (when (//unsigned.u1 id)
     {try.#Success register}
     (at ..monad in register)
     
@@ -696,7 +696,7 @@
   [(def .public (<name> local)
      (-> Nat (Bytecode Any))
      (with_expansions [<specials>' (template.spliced <specials>)]
-       (`` (case local
+       (`` (when local
              (,, (with_template [<case> <instruction> <registry>]
                    [<case> (..bytecode $0 <size> <registry> <instruction> [])]
                    
@@ -736,7 +736,7 @@
   [(def .public (<name> local)
      (-> Nat (Bytecode Any))
      (with_expansions [<specials>' (template.spliced <specials>)]
-       (`` (case local
+       (`` (when local
              (,, (with_template [<case> <instruction> <registry>]
                    [<case> (..bytecode <size> $0 <registry> <instruction> [])]
                    
@@ -815,7 +815,7 @@
 
 (def (resolve_label label resolver)
   (-> Label Resolver (Try [Stack Address]))
-  (case (dictionary.value label resolver)
+  (when (dictionary.value label resolver)
     {.#Some [actual {.#Some address}]}
     {try.#Success [actual address]}
 
@@ -828,7 +828,7 @@
 
 (def (acknowledge_label stack label tracker)
   (-> Stack Label Tracker Tracker)
-  (case (dictionary.value label (the #known tracker))
+  (when (dictionary.value label (the #known tracker))
     {.#Some _}
     tracker
 
@@ -857,7 +857,7 @@
                                (try|do _ (exception.assertion ..mismatched_environments [(symbol <instruction>) label @here expected actual]
                                                               (at /stack.equivalence = expected actual)))
                                (try|do jump (..jump @from @to))
-                               (case jump
+                               (when jump
                                  {.#Left jump}
                                  (exception.except ..cannot_do_a_big_jump [label @from jump])
 
@@ -901,12 +901,12 @@
                              (..acknowledge_label actual label)
                              (has #program_counter program_counter'))]
                         [(function (_ resolver)
-                           (case (dictionary.value label resolver)
+                           (when (dictionary.value label resolver)
                              {.#Some [expected {.#Some @to}]}
                              (<| (try|do _ (exception.assertion ..mismatched_environments [(symbol <instruction>) label @here expected actual]
                                                                 (at /stack.equivalence = expected actual)))
                                  (try|do jump (..jump @from @to))
-                                 (case jump
+                                 (when jump
                                    {.#Left jump}
                                    <on_long_jump>
 
@@ -931,7 +931,7 @@
 
 (def (big_jump jump)
   (-> Any_Jump Big_Jump)
-  (case jump
+  (when jump
     {.#Left big}
     big
 
@@ -957,7 +957,7 @@
                         (let [get (is (-> Label (Maybe [Stack (Maybe Address)]))
                                       (function (_ label)
                                         (dictionary.value label resolver)))]
-                          (case (do [! maybe.monad]
+                          (when (do [! maybe.monad]
                                   [@default (|> default get (monad.then ! product.right))
                                    @at_minimum (|> at_minimum get (monad.then ! product.right))]
                                   (|> afterwards
@@ -999,7 +999,7 @@
                         (let [get (is (-> Label (Maybe [Stack (Maybe Address)]))
                                       (function (_ label)
                                         (dictionary.value label resolver)))]
-                          (case (do [! maybe.monad]
+                          (when (do [! maybe.monad]
                                   [@default (|> default get (monad.then ! product.right))]
                                   (|> cases
                                       (monad.each ! (|>> product.right get))
@@ -1050,7 +1050,7 @@
   (-> (Type Object) U1 (Bytecode Any))
   (do ..monad
     [_ (is (Bytecode Any)
-           (case (|> dimensions //unsigned.value)
+           (when (|> dimensions //unsigned.value)
              0 (..except ..multiarray_cannot_be_zero_dimensional [class])
              _ (in [])))
      index (..lifted (//constant/pool.class (//name.internal (..reflection class))))]
@@ -1162,9 +1162,9 @@
   (All (_ pre post)
     (-> (Bytecode pre) (Bytecode post) (Bytecode post)))
   (function (_ state)
-    (case (pre state)
+    (when (pre state)
       {try.#Success [state' [left _]]}
-      (case (post state')
+      (when (post state')
         {try.#Success [state'' [right it]]}
         {try.#Success [state'' [(relative#composite left right) it]]}
 
diff --git a/stdlib/source/library/lux/meta/target/jvm/bytecode/environment.lux b/stdlib/source/library/lux/meta/target/jvm/bytecode/environment.lux
index 49e3455f4..dd33b7853 100644
--- a/stdlib/source/library/lux/meta/target/jvm/bytecode/environment.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/bytecode/environment.lux
@@ -53,7 +53,7 @@
 
 (def .public (stack environment)
   (-> Environment (Try Stack))
-  (case (the ..#stack environment)
+  (when (the ..#stack environment)
     {.#Some stack}
     {try.#Success stack}
 
@@ -72,7 +72,7 @@
 
 (def .public (continue expected environment)
   (-> Stack Environment (Try [Stack Environment]))
-  (case (the ..#stack environment)
+  (when (the ..#stack environment)
     {.#Some actual}
     (if (at /stack.equivalence = expected actual)
       {try.#Success [actual environment]}
diff --git a/stdlib/source/library/lux/meta/target/jvm/bytecode/instruction.lux b/stdlib/source/library/lux/meta/target/jvm/bytecode/instruction.lux
index 9dc19ed00..573424e12 100644
--- a/stdlib/source/library/lux/meta/target/jvm/bytecode/instruction.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/bytecode/instruction.lux
@@ -608,7 +608,7 @@
                                                  maximum (///signed.+/4 minimum amount_of_afterwards)]
                                                 (in (let [_ (binary.has_8! offset (hex "AA") binary)
                                                           offset (n.+ (///unsigned.value ..opcode_size) offset)
-                                                          _ (case padding
+                                                          _ (when padding
                                                               3 (|> binary
                                                                     (binary.has_8! offset 0)
                                                                     (binary.has_16! (++ offset) 0))
@@ -624,7 +624,7 @@
                                                       (loop (again [offset (n.+ (///unsigned.value ..integer_size) offset)
                                                                     afterwards (is (List Big_Jump)
                                                                                    {.#Item at_minimum afterwards})])
-                                                        (case afterwards
+                                                        (when afterwards
                                                           {.#End}
                                                           binary
                                                           
@@ -668,7 +668,7 @@
                                              [(n.+ lookupswitch_size offset)
                                               (let [_ (binary.has_8! offset (hex "AB") binary)
                                                     offset (n.+ (///unsigned.value ..opcode_size) offset)
-                                                    _ (case padding
+                                                    _ (when padding
                                                         3 (|> binary
                                                               (binary.has_8! offset 0)
                                                               (binary.has_16! (++ offset) 0))
@@ -681,7 +681,7 @@
                                                     _ (binary.has_32! offset amount_of_cases binary)]
                                                 (loop (again [offset (n.+ (///unsigned.value ..integer_size) offset)
                                                               cases cases])
-                                                  (case cases
+                                                  (when cases
                                                     {.#End}
                                                     binary
                                                     
diff --git a/stdlib/source/library/lux/meta/target/jvm/class.lux b/stdlib/source/library/lux/meta/target/jvm/class.lux
index bd9fdd41b..1a5b3a1d8 100644
--- a/stdlib/source/library/lux/meta/target/jvm/class.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/class.lux
@@ -103,7 +103,7 @@
            [classes (install_classes this super interfaces)
             =fields (monad.all ! fields)
             =methods (monad.all ! methods)
-            @signature (case signature
+            @signature (when signature
                          {.#Some signature}
                          (at ! each (|>> {.#Some}) (//attribute.signature signature))
 
@@ -120,7 +120,7 @@
          #interfaces @interfaces
          #fields (sequence.of_list =fields)
          #methods (sequence.of_list =methods)
-         #attributes (case @signature
+         #attributes (when @signature
                        {.#Some @signature}
                        (sequence.suffix @signature attributes)
 
diff --git a/stdlib/source/library/lux/meta/target/jvm/constant.lux b/stdlib/source/library/lux/meta/target/jvm/constant.lux
index a56a74c11..d05df9511 100644
--- a/stdlib/source/library/lux/meta/target/jvm/constant.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/constant.lux
@@ -171,7 +171,7 @@
 
 (def .public (size constant)
   (-> Constant Nat)
-  (case constant
+  (when constant
     (^.or {#Long _} {#Double _})
     2
 
@@ -184,7 +184,7 @@
   ... version below as soon as the new format for variants is implemented.
   (implementation
    (def (= reference sample)
-     (case [reference sample]
+     (when [reference sample]
        (^.with_template [<tag> <equivalence>]
          [[{<tag> reference} {<tag> sample}]
           (at <equivalence> = reference sample)])
@@ -242,7 +242,7 @@
                                        ... TODO: Invoke_Dynamic
                                        )]
     (function (_ value)
-      (case value
+      (when value
         (^.with_template [<case> <tag> <format>]
           [{<case> value}
            (binaryF#composite (/tag.format <tag>)
diff --git a/stdlib/source/library/lux/meta/target/jvm/constant/pool.lux b/stdlib/source/library/lux/meta/target/jvm/constant/pool.lux
index d3a8c2546..759d88314 100644
--- a/stdlib/source/library/lux/meta/target/jvm/constant/pool.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/constant/pool.lux
@@ -49,7 +49,7 @@
   (implementation
    (def (each $ it)
      (|>> it
-          (pipe.case
+          (pipe.when
             {try.#Success [state output]}
             {try.#Success [state ($ output)]}
             
@@ -68,7 +68,7 @@
    
    (def (conjoint it)
      (function (_ state)
-       (case (it state)
+       (when (it state)
          {try.#Success [state' it']}
          (it' state')
 
@@ -78,7 +78,7 @@
 
 (def try|each
   (template (_ <binding> <value> <body>)
-    [(case <value>
+    [(when <value>
        {try.#Success <binding>}
        <body>
 
@@ -96,9 +96,9 @@
            <value>' <value>]
        (with_expansions [<try_again> (these (again (.++ idx)))]
          (loop (again [idx 0])
-           (case (sequence.item idx pool)
+           (when (sequence.item idx pool)
              {try.#Success entry}
-             (case entry
+             (when entry
                [index {<tag> reference}]
                (if (at <equivalence> = reference <value>')
                  {try.#Success [[current pool]
@@ -127,7 +127,7 @@
 
 (def /|each
   (template (_ <state> <binding> <value> <body>)
-    [(case (<value> <state>)
+    [(when (<value> <state>)
        {try.#Success [<state> <binding>]}
        <body>
 
diff --git a/stdlib/source/library/lux/meta/target/jvm/field.lux b/stdlib/source/library/lux/meta/target/jvm/field.lux
index e0561b457..49c60849e 100644
--- a/stdlib/source/library/lux/meta/target/jvm/field.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/field.lux
@@ -73,7 +73,7 @@
     (in [#modifier modifier
          #name @name
          #descriptor @descriptor
-         #attributes (case @signature
+         #attributes (when @signature
                        {.#Some @signature}
                        (sequence.suffix @signature attributes)
                        
diff --git a/stdlib/source/library/lux/meta/target/jvm/loader.lux b/stdlib/source/library/lux/meta/target/jvm/loader.lux
index 05d45cfad..c8d70c482 100644
--- a/stdlib/source/library/lux/meta/target/jvm/loader.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/loader.lux
@@ -117,9 +117,9 @@
                                  "throws" [java/lang/ClassNotFoundException]
                                  (let [class_name (as Text class_name)
                                        classes (|> library atom.read! io.run!)]
-                                   (case (dictionary.value class_name classes)
+                                   (when (dictionary.value class_name classes)
                                      {.#Some bytecode}
-                                     (case (..define class_name bytecode (<| <cast> self))
+                                     (when (..define class_name bytecode (<| <cast> self))
                                        {try.#Success class}
                                        (as_expected class)
 
diff --git a/stdlib/source/library/lux/meta/target/jvm/method.lux b/stdlib/source/library/lux/meta/target/jvm/method.lux
index 3db1be9bc..ec4780b0f 100644
--- a/stdlib/source/library/lux/meta/target/jvm/method.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/method.lux
@@ -63,10 +63,10 @@
                       attributes)
                     (monad.all !)
                     (at ! each sequence.of_list))
-     attributes (case code
+     attributes (when code
                   {.#Some code}
                   (do !
-                    [environment (case (if (//modifier.has? static modifier)
+                    [environment (when (if (//modifier.has? static modifier)
                                          (//environment.static type)
                                          (//environment.virtual type))
                                    {try.#Success environment}
diff --git a/stdlib/source/library/lux/meta/target/jvm/reflection.lux b/stdlib/source/library/lux/meta/target/jvm/reflection.lux
index 0ee71e599..a33bc6507 100644
--- a/stdlib/source/library/lux/meta/target/jvm/reflection.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/reflection.lux
@@ -112,7 +112,7 @@
 
 (def .public (load class_loader name)
   (-> java/lang/ClassLoader External (Try (java/lang/Class java/lang/Object)))
-  (case (java/lang/Class::forName name false class_loader)
+  (when (java/lang/Class::forName name false class_loader)
     {try.#Failure _}
     (exception.except ..unknown_class [name])
 
@@ -130,7 +130,7 @@
   (-> (-> java/lang/reflect/Type (Try (/.Type Parameter)))
       java/lang/reflect/Type
       (Try (/.Type Class)))
-  (<| (case (ffi.as java/lang/Class reflection)
+  (<| (when (ffi.as java/lang/Class reflection)
         {.#Some class}
         (let [class_name (|> class
                              (as (java/lang/Class java/lang/Object))
@@ -151,10 +151,10 @@
                 (exception.except ..not_a_class [reflection])
                 {try.#Success (/.class class_name (list))})))
         _)
-      (case (ffi.as java/lang/reflect/ParameterizedType reflection)
+      (when (ffi.as java/lang/reflect/ParameterizedType reflection)
         {.#Some reflection}
         (let [raw (java/lang/reflect/ParameterizedType::getRawType reflection)]
-          (case (ffi.as java/lang/Class raw)
+          (when (ffi.as java/lang/Class raw)
             {.#Some raw'}
             (let [! try.monad]
               (|> reflection
@@ -175,19 +175,19 @@
 (def .public (parameter type reflection)
   (-> (-> java/lang/reflect/Type (Try (/.Type Value)))
       (-> java/lang/reflect/Type (Try (/.Type Parameter))))
-  (<| (case (ffi.as java/lang/reflect/TypeVariable reflection)
+  (<| (when (ffi.as java/lang/reflect/TypeVariable reflection)
         {.#Some reflection}
         {try.#Success (/.var (java/lang/reflect/TypeVariable::getName reflection))}
         _)
-      (case (ffi.as java/lang/reflect/WildcardType reflection)
+      (when (ffi.as java/lang/reflect/WildcardType reflection)
         {.#Some reflection}
         ... TODO: Instead of having single lower/upper bounds, should
         ... allow for multiple ones.
-        (case [(array.item 0 (java/lang/reflect/WildcardType::getLowerBounds reflection))
+        (when [(array.item 0 (java/lang/reflect/WildcardType::getLowerBounds reflection))
                (array.item 0 (java/lang/reflect/WildcardType::getUpperBounds reflection))]
           (^.with_template [<pattern> <kind>]
             [<pattern>
-             (case (ffi.as java/lang/reflect/GenericArrayType bound)
+             (when (ffi.as java/lang/reflect/GenericArrayType bound)
                {.#Some it}
                ... TODO: Array bounds should not be "erased" as they
                ... are right now.
@@ -201,14 +201,14 @@
           _
           {try.#Success /.wildcard})
         _)
-      (case (ffi.as java/lang/reflect/GenericArrayType reflection)
+      (when (ffi.as java/lang/reflect/GenericArrayType reflection)
         {.#Some reflection}
         (|> reflection
             java/lang/reflect/GenericArrayType::getGenericComponentType
             type
             (at try.monad each /.array))
         _)
-      (case (ffi.as java/lang/Class reflection)
+      (when (ffi.as java/lang/Class reflection)
         {.#Some class}
         (if (java/lang/Class::isArray class)
           (|> class
@@ -221,7 +221,7 @@
 
 (def .public (type reflection)
   (-> java/lang/reflect/Type (Try (/.Type Value)))
-  (<| (case (ffi.as java/lang/Class reflection)
+  (<| (when (ffi.as java/lang/Class reflection)
         {.#Some reflection}
         (let [class_name (|> reflection
                              (as (java/lang/Class java/lang/Object))
@@ -254,7 +254,7 @@
 (def .public (return reflection)
   (-> java/lang/reflect/Type (Try (/.Type Return)))
   (with_expansions [<else> (these (..type reflection))]
-    (case (ffi.as java/lang/Class reflection)
+    (when (ffi.as java/lang/Class reflection)
       {.#Some class}
       (let [class_name (|> reflection
                            (as (java/lang/Class java/lang/Object))
@@ -289,8 +289,8 @@
 
 (def .public (correspond class type)
   (-> (java/lang/Class java/lang/Object) Type (Try Mapping))
-  (case type
-    {.#Primitive array.type_name (list :member:)}
+  (when type
+    {.#Primitive array.primitive (list :member:)}
     (if (java/lang/Class::isArray class)
       (correspond (java/lang/Class::getComponentType class)
                   :member:)
@@ -317,7 +317,7 @@
     (correspond class anonymousT)
 
     {.#Apply inputT abstractionT}
-    (case (type.applied (list inputT) abstractionT)
+    (when (type.applied (list inputT) abstractionT)
       {.#Some outputT}
       (correspond class outputT)
 
@@ -349,7 +349,7 @@
 
 (def .public (field field target)
   (-> Text (java/lang/Class java/lang/Object) (Try java/lang/reflect/Field))
-  (case (java/lang/Class::getDeclaredField field target)
+  (when (java/lang/Class::getDeclaredField field target)
     {try.#Success field}
     (let [owner (java/lang/reflect/Field::getDeclaringClass field)]
       (if (same? owner target)
@@ -372,7 +372,7 @@
      (do [! try.monad]
        [fieldJ (..field field class)
         .let [modifiers (java/lang/reflect/Field::getModifiers fieldJ)]]
-       (case (java/lang/reflect/Modifier::isStatic modifiers)
+       (when (java/lang/reflect/Modifier::isStatic modifiers)
          <then?> (|> fieldJ
                      java/lang/reflect/Field::getGenericType
                      ..type
diff --git a/stdlib/source/library/lux/meta/target/jvm/type/lux.lux b/stdlib/source/library/lux/meta/target/jvm/type/lux.lux
index 3af93e1b5..4f6d9076f 100644
--- a/stdlib/source/library/lux/meta/target/jvm/type/lux.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/type/lux.lux
@@ -121,7 +121,7 @@
   (-> Mapping (Parser (Check Type)))
   (do <>.monad
     [var //parser.var']
-    (in (case (dictionary.value var mapping)
+    (in (when (dictionary.value var mapping)
           {.#None}
           (check.except ..unknown_var [var])
           
@@ -174,7 +174,7 @@
 (def array
   (-> (Parser (Check Type)) (Parser (Check Type)))
   (|>> (<>#each (check#each (function (_ elementT)
-                              (case elementT
+                              (when elementT
                                 {.#Primitive name {.#End}}
                                 (if (`` (or (,, (with_template [<reflection>]
                                                   [(text#= (//reflection.reflection <reflection>) name)]
@@ -230,7 +230,7 @@
 
 (def .public (check operation input)
   (All (_ a) (-> (Parser (Check a)) Text (Check a)))
-  (case (<text>.result operation input)
+  (when (<text>.result operation input)
     {try.#Success check}
     check
     
diff --git a/stdlib/source/library/lux/meta/target/jvm/type/signature.lux b/stdlib/source/library/lux/meta/target/jvm/type/signature.lux
index 6afc33607..96a912cde 100644
--- a/stdlib/source/library/lux/meta/target/jvm/type/signature.lux
+++ b/stdlib/source/library/lux/meta/target/jvm/type/signature.lux
@@ -95,7 +95,7 @@
     (abstraction
      (format //descriptor.class_prefix
              (|> name ///name.internal ///name.read)
-             (case parameters
+             (when parameters
                {.#End}
                ""
 
@@ -130,7 +130,7 @@
 
   (def var_declaration/*
     (-> (List (Signature Var)) Text)
-    (|>> (pipe.case
+    (|>> (pipe.when
            {.#End}
            ""
            
diff --git a/stdlib/source/library/lux/meta/target/lua.lux b/stdlib/source/library/lux/meta/target/lua.lux
index 1ea2f196c..8168b065b 100644
--- a/stdlib/source/library/lux/meta/target/lua.lux
+++ b/stdlib/source/library/lux/meta/target/lua.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except Location Code Label int if function or and not let local comment the)
+  [lux (.except Location Code Label int if function or and not let local comment the when)
    [abstract
     [equivalence (.only Equivalence)]
     [hash (.only Hash)]
@@ -91,7 +91,7 @@
 
   (def .public boolean
     (-> Bit Literal)
-    (|>> (pipe.case
+    (|>> (pipe.when
            #0 "false"
            #1 "true")
          abstraction))
@@ -375,7 +375,7 @@
 
 (def arity_inputs
   (syntax (_ [arity <code>.nat])
-    (in (case arity
+    (in (.when arity
           0 (.list)
           _ (|> (-- arity)
                 (enum.range n.enum 0)
diff --git a/stdlib/source/library/lux/meta/target/php.lux b/stdlib/source/library/lux/meta/target/php.lux
index cb7870fd2..748d852c2 100644
--- a/stdlib/source/library/lux/meta/target/php.lux
+++ b/stdlib/source/library/lux/meta/target/php.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except Location Code Global Label static int if cond or and not comment for try global the parameter)
+  [lux (.except Location Code Global Label static int if cond or and not comment for try global the parameter when)
    [abstract
     [equivalence (.only Equivalence)]
     [hash (.only Hash)]
@@ -134,7 +134,7 @@
 
   (def .public bool
     (-> Bit Literal)
-    (|>> (pipe.case
+    (|>> (pipe.when
            #0 "false"
            #1 "true")
          abstraction))
@@ -220,7 +220,7 @@
 
   (def .public (closure uses arguments body!)
     (-> (List Argument) (List Argument) Statement Literal)
-    (let [uses (case uses
+    (let [uses (.when uses
                  {.#End}
                  ""
 
@@ -234,7 +234,7 @@
 
   (def arity_inputs
     (syntax (_ [arity <code>.nat])
-      (in (case arity
+      (in (.when arity
             0 (.list)
             _ (|> (-- arity)
                   (enum.range n.enum 0)
diff --git a/stdlib/source/library/lux/meta/target/python.lux b/stdlib/source/library/lux/meta/target/python.lux
index b3c874f26..93014c3e4 100644
--- a/stdlib/source/library/lux/meta/target/python.lux
+++ b/stdlib/source/library/lux/meta/target/python.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except Location Code not or and list if int comment exec try the is def)
+  [lux (.except Location Code not or and list if int comment exec try the is def when)
    ["[0]" ffi]
    [abstract
     [equivalence (.only Equivalence)]
@@ -132,7 +132,7 @@
 
   (.def .public bool
     (-> Bit Literal)
-    (|>> (pipe.case
+    (|>> (pipe.when
            #0 "False"
            #1 "True")
          abstraction))
@@ -370,7 +370,7 @@
     (abstraction
      (format "while " (representation test) ":"
              (..nested (representation body!))
-             (case else!
+             (.when else!
                {.#Some else!}
                (format \n+ "else:"
                        (..nested (representation else!)))
@@ -423,7 +423,7 @@
 
   (.def .public (exec globals code)
     (-> (Maybe (Expression Any)) (Expression Any) (Statement Any))
-    (let [extra (case globals
+    (let [extra (.when globals
                   {.#Some globals}
                   (.list globals)
 
@@ -453,7 +453,7 @@
 
 (.def arity_inputs
   (syntax (_ [arity <code>.nat])
-    (in (case arity
+    (in (.when arity
           0 (.list)
           _ (|> (-- arity)
                 (enum.range n.enum 0)
diff --git a/stdlib/source/library/lux/meta/target/r.lux b/stdlib/source/library/lux/meta/target/r.lux
index f425f584b..7da2c28bd 100644
--- a/stdlib/source/library/lux/meta/target/r.lux
+++ b/stdlib/source/library/lux/meta/target/r.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except Code or and list if function cond not int)
+  [lux (.except Code or and list if function cond not int when)
    [control
     ["[0]" pipe]
     ["[0]" function]
@@ -113,7 +113,7 @@
 
   (def .public bool
     (-> Bit Expression)
-    (|>> (pipe.case
+    (|>> (pipe.when
            #0 "FALSE"
            #1 "TRUE")
          abstraction))
@@ -211,7 +211,7 @@
 
   (def arity_inputs
     (syntax (_ [arity <code>.nat])
-      (in (case arity
+      (in (.when arity
             0 (.list)
             _ (|> arity
                   list.indices
diff --git a/stdlib/source/library/lux/meta/target/ruby.lux b/stdlib/source/library/lux/meta/target/ruby.lux
index 179d0182c..628c02eb3 100644
--- a/stdlib/source/library/lux/meta/target/ruby.lux
+++ b/stdlib/source/library/lux/meta/target/ruby.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except Location Code static int if function or and not comment local global symbol the)
+  [lux (.except Location Code static int if function or and not comment local global symbol the when)
    [abstract
     [equivalence (.only Equivalence)]
     [hash (.only Hash)]
@@ -153,7 +153,7 @@
 
   (def .public bool
     (-> Bit Literal)
-    (|>> (pipe.case
+    (|>> (pipe.when
            #0 "false"
            #1 "true")
          abstraction))
@@ -247,7 +247,7 @@
                         (list#each (|>> representation))
                         (text.interposed ..input_separator)
                         (text.enclosed ["(" ")"]))
-          block (case block
+          block (.when block
                   {.#None}
                   ""
                   
@@ -395,7 +395,7 @@
   (def .public (lambda name block)
     (-> (Maybe LVar) Block Literal)
     (let [proc (format "lambda " (..block block))]
-      (|> (case name
+      (|> (.when name
             {.#None}
             proc
             
@@ -483,7 +483,7 @@
 
 (def arity_inputs
   (syntax (_ [arity <code>.nat])
-    (in (case arity
+    (in (.when arity
           0 (.list)
           _ (|> (-- arity)
                 (enum.range n.enum 0)
diff --git a/stdlib/source/library/lux/meta/target/scheme.lux b/stdlib/source/library/lux/meta/target/scheme.lux
index 86b9c5921..51a712a6f 100644
--- a/stdlib/source/library/lux/meta/target/scheme.lux
+++ b/stdlib/source/library/lux/meta/target/scheme.lux
@@ -1,6 +1,6 @@
 (.require
  [library
-  [lux (.except Code int or and if cond let symbol)
+  [lux (.except Code int or and if cond let symbol when)
    [abstract
     [equivalence (.only Equivalence)]
     [hash (.only Hash)]]
@@ -81,9 +81,9 @@
 
   (def (arguments [mandatory rest])
     (-> Arguments (Code Any))
-    (case rest
+    (.when rest
       {.#Some rest}
-      (case mandatory
+      (.when mandatory
         {.#End}
         rest
 
@@ -108,7 +108,7 @@
 
   (def .public bool
     (-> Bit Computation)
-    (|>> (pipe.case
+    (|>> (pipe.when
            #0 "#f"
            #1 "#t")
          abstraction))
@@ -163,7 +163,7 @@
   (def form
     (-> (List (Code Any)) Code)
     (.let [nested_new_line (format \n+ text.tab)]
-      (|>> (pipe.case
+      (|>> (pipe.when
              {.#End}
              (abstraction "()")
              
@@ -375,7 +375,7 @@
   (def .public (guard variable clauses else body)
     (-> Var (List [Expression Expression]) (Maybe Expression) Expression Computation)
     (..form (list (..var "guard")
-                  (..form (|> (case else
+                  (..form (|> (.when else
                                 {.#None}
                                 (list)
                                 
diff --git a/stdlib/source/library/lux/meta/type.lux b/stdlib/source/library/lux/meta/type.lux
index 70181ea04..a2bec39bf 100644
--- a/stdlib/source/library/lux/meta/type.lux
+++ b/stdlib/source/library/lux/meta/type.lux
@@ -32,7 +32,7 @@
      (-> Type [Nat Type])
      (loop (again [num_args 0
                    type type])
-       (case type
+       (when type
          {<tag> env sub_type}
          (again (++ num_args) sub_type)
 
@@ -45,7 +45,7 @@
 
 (def .public (flat_function type)
   (-> Type [(List Type) Type])
-  (case type
+  (when type
     {.#Function in out'}
     (.let [[ins out] (flat_function out')]
       [(list.partial in ins) out])
@@ -55,7 +55,7 @@
 
 (def .public (flat_application type)
   (-> Type [Type (List Type)])
-  (case type
+  (when type
     {.#Apply arg func'}
     (.let [[func args] (flat_application func')]
       [func (list#composite args (list arg))])
@@ -66,7 +66,7 @@
 (with_template [<name> <tag>]
   [(def .public (<name> type)
      (-> Type (List Type))
-     (case type
+     (when type
        {<tag> left right}
        (list.partial left (<name> right))
 
@@ -79,7 +79,7 @@
 
 (`` (def .public (format type)
       (-> Type Text)
-      (case type
+      (when type
         {.#Primitive name params}
         (all text#composite
              "(Primitive "
@@ -139,7 +139,7 @@
 ... https://en.wikipedia.org/wiki/Lambda_calculus#%CE%B2-reduction
 (`` (def (reduced env type)
       (-> (List Type) Type Type)
-      (case type
+      (when type
         {.#Primitive name params}
         {.#Primitive name (list#each (reduced env) params)}
         
@@ -152,7 +152,7 @@
         
         (,, (with_template [<tag>]
               [{<tag> old_env def}
-               (case old_env
+               (when old_env
                  {.#End}
                  {<tag> env def}
 
@@ -187,7 +187,7 @@
                   ... TODO: Remove this once JPHP is gone.
                   false
                   (same? x y))
-             (case [x y]
+             (when [x y]
                [{.#Primitive xname xparams} {.#Primitive yname yparams}]
                (and (text#= xname yname)
                     (n.= (list.size yparams) (list.size xparams))
@@ -237,12 +237,12 @@
 
 (`` (def .public (applied params func)
       (-> (List Type) Type (Maybe Type))
-      (case params
+      (when params
         {.#End}
         {.#Some func}
 
         {.#Item param params'}
-        (case func
+        (when func
           (,, (with_template [<tag>]
                 [{<tag> env body}
                  (|> body
@@ -263,7 +263,7 @@
 
 (`` (def .public (code type)
       (-> Type Code)
-      (case type
+      (when type
         {.#Primitive name params}
         (` {.#Primitive (, (code.text name))
                         (.list (,* (list#each code params)))})
@@ -300,7 +300,7 @@
 
 (def .public (de_aliased type)
   (-> Type Type)
-  (case type
+  (when type
     {.#Named _ {.#Named name type'}}
     (de_aliased {.#Named name type'})
 
@@ -309,7 +309,7 @@
 
 (def .public (anonymous type)
   (-> Type Type)
-  (case type
+  (when type
     {.#Named name type'}
     (anonymous type')
 
@@ -319,7 +319,7 @@
 (with_template [<name> <base> <ctor>]
   [(def .public (<name> types)
      (-> (List Type) Type)
-     (case types
+     (when types
        {.#End}
        <base>
 
@@ -335,7 +335,7 @@
 
 (def .public (function inputs output)
   (-> (List Type) Type Type)
-  (case inputs
+  (when inputs
     {.#End}
     output
 
@@ -344,7 +344,7 @@
 
 (def .public (application params quant)
   (-> (List Type) Type Type)
-  (case params
+  (when params
     {.#End}
     quant
 
@@ -354,7 +354,7 @@
 (with_template [<name> <tag>]
   [(def .public (<name> size body)
      (-> Nat Type Type)
-     (case size
+     (when size
        0 body
        _  (|> body (<name> (-- size)) {<tag> (list)})))]
 
@@ -364,7 +364,7 @@
 
 (`` (def .public (quantified? type)
       (-> Type Bit)
-      (case type
+      (when type
         {.#Named [module name] _type}
         (quantified? _type)
 
@@ -385,7 +385,7 @@
 
 (def .public (array depth element_type)
   (-> Nat Type Type)
-  (case depth
+  (when depth
     0 element_type
     _ (|> element_type
           (array (-- depth))
@@ -395,7 +395,7 @@
 (def .public (flat_array type)
   (-> Type [Nat Type])
   (with_expansions [<default> [0 type]]
-    (case type
+    (when type
       {.#Primitive name (list element_type)}
       (if (text#= array.primitive name)
         (.let [[depth element_type] (flat_array element_type)]
@@ -423,7 +423,7 @@
   (syntax (_ [input (<>.or (<>.and <code>.symbol
                                    (<>.maybe (<>.after (<code>.this_symbol ..secret_marker) <code>.any)))
                            <code>.any)])
-    (case input
+    (when input
       {.#Left [valueN valueC]}
       (do meta.monad
         [location meta.location
@@ -431,7 +431,7 @@
          .let [_ ("lux io log"
                   (all text#composite
                        (symbol#encoded (symbol ..log!)) " " (location.format location) text.new_line
-                       "Expression: " (case valueC
+                       "Expression: " (when valueC
                                         {.#Some valueC}
                                         (code.format valueC)
                                         
@@ -459,7 +459,7 @@
       (.let [casterC (` (is (All ((, g!_) (,* (list#each code.local type_vars)))
                               (-> (, input) (, output)))
                             (|>> as_expected)))]
-        (case value
+        (when value
           {.#None}
           (in (list casterC))
           
@@ -511,7 +511,7 @@
       (.function (again it)
         (if (at ..equivalence = before it)
           after
-          (case it
+          (when it
             {.#Primitive name co_variant}
             {.#Primitive name (list#each again co_variant)}
 
diff --git a/stdlib/source/library/lux/meta/type/check.lux b/stdlib/source/library/lux/meta/type/check.lux
index 90fb49156..184864469 100644
--- a/stdlib/source/library/lux/meta/type/check.lux
+++ b/stdlib/source/library/lux/meta/type/check.lux
@@ -80,7 +80,7 @@
   (implementation
    (def (each f fa)
      (function (_ context)
-       (case (fa context)
+       (when (fa context)
          {try.#Success [context' output]}
          {try.#Success [context' (f output)]}
 
@@ -94,9 +94,9 @@
 
    (def (on fa ff)
      (function (_ context)
-       (case (ff context)
+       (when (ff context)
          {try.#Success [context' f]}
-         (case (fa context')
+         (when (fa context')
            {try.#Success [context'' a]}
            {try.#Success [context'' (f a)]}
 
@@ -119,9 +119,9 @@
 
    (def (conjoint ffa)
      (function (_ context)
-       (case (ffa context)
+       (when (ffa context)
          {try.#Success [context' fa]}
-         (case (fa context')
+         (when (fa context')
            {try.#Success [context'' a]}
            {try.#Success [context'' a]}
 
@@ -141,7 +141,7 @@
 
 (def (var::get id property_list)
   (-> Var Type_Vars (Maybe (Maybe Type)))
-  (case property_list
+  (when property_list
     {.#Item [var_id var_type]
             property_list'}
     (if (!n#= id var_id)
@@ -153,7 +153,7 @@
 
 (def (var::put id value property_list)
   (-> Var (Maybe Type) Type_Vars Type_Vars)
-  (case property_list
+  (when property_list
     {.#End}
     (list [id value])
 
@@ -167,7 +167,7 @@
 
 (def .public (result context proc)
   (All (_ a) (-> Type_Context (Check a) (Try a)))
-  (case (proc context)
+  (when (proc context)
     {try.#Success [context' output]}
     {try.#Success output}
 
@@ -201,7 +201,7 @@
   [(def .public (<name> id)
      (-> Var (Check <outputT>))
      (function (_ context)
-       (case (|> context (the .#var_bindings) (var::get id))
+       (when (|> context (the .#var_bindings) (var::get id))
          (^.or {.#Some {.#Some {.#Var _}}}
                {.#Some {.#None}})
          {try.#Success [context <fail>]}
@@ -220,7 +220,7 @@
   (-> Var (Check Type))
   (do ..monad
     [?type (peek id)]
-    (case ?type
+    (when ?type
       {.#Some type}
       (in type)
 
@@ -230,7 +230,7 @@
 (def (bound id)
   (-> Var (Check Type))
   (function (_ context)
-    (case (|> context (the .#var_bindings) (var::get id))
+    (when (|> context (the .#var_bindings) (var::get id))
       {.#Some {.#Some bound}}
       {try.#Success [context bound]}
 
@@ -243,7 +243,7 @@
 (def .public (bind type id)
   (-> Type Var (Check Any))
   (function (_ context)
-    (case (|> context (the .#var_bindings) (var::get id))
+    (when (|> context (the .#var_bindings) (var::get id))
       {.#Some {.#None}}
       {try.#Success [(revised .#var_bindings (var::put id {.#Some type}) context)
                      []]}
@@ -257,7 +257,7 @@
 (def (re_bind' ?type id)
   (-> (Maybe Type) Var (Check Any))
   (function (_ context)
-    (case (|> context (the .#var_bindings) (var::get id))
+    (when (|> context (the .#var_bindings) (var::get id))
       {.#Some _}
       {try.#Success [(revised .#var_bindings (var::put id ?type) context)
                      []]}
@@ -280,11 +280,11 @@
 
 (def (on argT funcT)
   (-> Type Type (Check Type))
-  (case funcT
+  (when funcT
     {.#Var func_id}
     (do ..monad
       [?funcT' (peek func_id)]
-      (case ?funcT'
+      (when ?funcT'
         {.#Some funcT'}
         (on argT funcT')
 
@@ -297,7 +297,7 @@
       (on argT funcT''))
 
     _
-    (case (//.applied (list argT) funcT)
+    (when (//.applied (list argT) funcT)
       {.#Some output}
       (check#in output)
 
@@ -309,9 +309,9 @@
   (function (_ context)
     (loop (again [current start
                   output (list start)])
-      (case (|> context (the .#var_bindings) (var::get current))
+      (when (|> context (the .#var_bindings) (var::get current))
         {.#Some {.#Some type}}
-        (case type
+        (when type
           {.#Var next}
           (if (!n#= start next)
             {try.#Success [context output]}
@@ -346,7 +346,7 @@
   (-> (List Var) Var (Check Type))
   (do [! ..monad]
     [:bound: (..peek @)]
-    (case :bound:
+    (when :bound:
       {.#Some :bound:}
       (in :bound:)
 
@@ -358,7 +358,7 @@
           (do !
             [.let [forbidden_aliases (set.of_list n.hash (list.partial @ aliases))
                    allowed_aliases (set.difference forbidden_aliases existing_aliases)]]
-            (case (set.list allowed_aliases)
+            (when (set.list allowed_aliases)
               {.#Item identity _}
               (in {.#Var identity})
               
@@ -387,7 +387,7 @@
   (-> Var (Check Any))
   (do [! ..monad]
     [ring (..ring' @)]
-    (case ring
+    (when ring
       (list)
       (in [])
       
@@ -400,7 +400,7 @@
         (erase! @me))
       
       (list.partial @prev _)
-      (case (list.reversed ring)
+      (when (list.reversed ring)
         (list.partial @me @next _)
         (do !
           [_ (re_bind {.#Var @next} @prev)
@@ -413,7 +413,7 @@
 (def .public (try it)
   (All (_ a) (-> (Check a) (Check (Try a))))
   (function (_ context)
-    (case (it context)
+    (when (it context)
       {try.#Success [context' output]}
       {try.#Success [context' {try.#Success output}]}
 
@@ -429,7 +429,7 @@
 (def (either left right)
   (All (_ a) (-> (Check a) (Check a) (Check a)))
   (function (_ context)
-    (case (left context)
+    (when (left context)
       {try.#Failure _}
       (right context)
 
@@ -483,7 +483,7 @@
     (do [! ..monad]
       [ebound (..try (..bound idE))
        abound (..try (..bound idA))]
-      (case [ebound abound]
+      (when [ebound abound]
         ... Link the 2 variables circularly
         [{try.#Failure _} {try.#Failure _}]
         (do !
@@ -492,7 +492,7 @@
 
         ... Interpose new variable between 2 existing links
         [{try.#Success etype} {try.#Failure _}]
-        (case etype
+        (when etype
           {.#Var targetE}
           (do !
             [_ (link/3 idA targetE idE)]
@@ -503,7 +503,7 @@
 
         ... Interpose new variable between 2 existing links
         [{try.#Failure _} {try.#Success atype}]
-        (case atype
+        (when atype
           {.#Var targetA}
           (do !
             [_ (link/3 idE targetA idA)]
@@ -513,7 +513,7 @@
           (check' assumptions {.#Var idE} atype))
 
         [{try.#Success etype} {try.#Success atype}]
-        (case [etype atype]
+        (when [etype atype]
           [{.#Var targetE} {.#Var targetA}]
           (do !
             [ringE (..ring idE)
@@ -551,7 +551,7 @@
   (-> (Checker Type) (Checker [Type Type]))
   (let [[expected_input expected_function] expected
         [actual_input actual_function] actual]
-    (case [expected_function actual_function]
+    (when [expected_function actual_function]
       [{.#Ex exE} {.#Ex exA}]
       (if (!n#= exE exA)
         (check' assumptions expected_input actual_input)
@@ -584,7 +584,7 @@
 
       [{.#Var id} _]
       (function (_ context)
-        (case ((do ..monad
+        (when ((do ..monad
                  [expected_function' (..read id)]
                  (check' assumptions {.#Apply expected_input expected_function'} {.#Apply actual}))
                context)
@@ -592,7 +592,7 @@
           {try.#Success output}
 
           {try.#Failure _}
-          (case actual_function
+          (when actual_function
             {.#UnivQ _ _}
             ((do ..monad
                [actual' (..on actual_input actual_function)]
@@ -615,7 +615,7 @@
 
       [_ {.#Var id}]
       (function (_ context)
-        (case ((do ..monad
+        (when ((do ..monad
                  [actual_function' (read id)]
                  (check' assumptions {.#Apply expected} {.#Apply actual_input actual_function'}))
                context)
@@ -648,7 +648,7 @@
            (same? expected actual))
     (check#in assumptions)
     (with_exception ..type_check_failed [expected actual]
-      (case [expected actual]
+      (when [expected actual]
         [{.#Var idE} {.#Var idA}]
         (check_vars check' assumptions idE idA)
         
@@ -710,7 +710,7 @@
           (loop (again [assumptions assumptions
                         e_params e_params
                         a_params a_params])
-            (case [e_params a_params]
+            (when [e_params a_params]
               [{.#End} {.#End}]
               (check#in assumptions)
               
@@ -756,7 +756,7 @@
 
 (def .public (subsumes? expected actual)
   (-> Type Type Bit)
-  (case (..result ..fresh_context
+  (when (..result ..fresh_context
                   (..check expected actual))
     {try.#Failure _}
     false
@@ -776,7 +776,7 @@
 
 (def .public (clean aliases inputT)
   (-> (List Var) Type (Check Type))
-  (case inputT
+  (when inputT
     {.#Primitive name paramsT+}
     (|> paramsT+
         (monad.each ..monad (clean aliases))
@@ -794,11 +794,11 @@
     ([.#Sum] [.#Product] [.#Function] [.#Apply])
 
     {.#Var @it}
-    (case aliases
+    (when aliases
       (list)
       (do ..monad
         [?actualT (..peek @it)]
-        (case ?actualT
+        (when ?actualT
           {.#Some actualT}
           (clean aliases actualT)
 
@@ -808,9 +808,9 @@
       _
       (do ..monad
         [:it: (..try (..identity aliases @it))]
-        (case :it:
+        (when :it:
           {try.#Success :it:}
-          (case :it:
+          (when :it:
             {.#Var _}
             (in inputT)
 
diff --git a/stdlib/source/library/lux/meta/type/implicit.lux b/stdlib/source/library/lux/meta/type/implicit.lux
index 835fff931..df5da5767 100644
--- a/stdlib/source/library/lux/meta/type/implicit.lux
+++ b/stdlib/source/library/lux/meta/type/implicit.lux
@@ -29,10 +29,10 @@
 
 (def (type_var id env)
   (-> Nat Type_Context (Meta Type))
-  (case (list.example (|>> product.left (n.= id))
+  (when (list.example (|>> product.left (n.= id))
                       (the .#var_bindings env))
     {.#Some [_ {.#Some type}]}
-    (case type
+    (when type
       {.#Var id'}
       (type_var id' env)
 
@@ -51,7 +51,7 @@
   (do ///.monad
     [raw_type (///.type var_name)
      compiler ///.compiler_state]
-    (case raw_type
+    (when raw_type
       {.#Var id}
       (type_var id (the .#type_context compiler))
 
@@ -60,12 +60,12 @@
 
 (def (member_type idx sig_type)
   (-> Nat Type (Check Type))
-  (case sig_type
+  (when sig_type
     {.#Named _ sig_type'}
     (member_type idx sig_type')
 
     {.#Apply arg func}
-    (case (//.applied (list arg) func)
+    (when (//.applied (list arg) func)
       {.#None}
       (check.failure (format "Cannot apply type " (%.type func) " to type " (%.type arg)))
 
@@ -84,7 +84,7 @@
 
 (def (member_name member)
   (-> Symbol (Meta Symbol))
-  (case member
+  (when member
     ["" simple_name]
     (///.either (do ///.monad
                   [member (///.normal member)
@@ -97,7 +97,7 @@
                    .let [tag_lists (|> tag_lists list#conjoint (list#each product.left) list#conjoint)
                          candidates (list.only (|>> product.right (text#= simple_name))
                                                tag_lists)]]
-                  (case candidates
+                  (when candidates
                     {.#End}
                     (///.failure (format "Unknown tag: " (%.symbol member)))
                     
@@ -181,7 +181,7 @@
 
 (def (on_argument arg func)
   (-> Type Type (Check Type))
-  (case func
+  (when func
     {.#Named _ func'}
     (on_argument arg func')
 
@@ -203,7 +203,7 @@
 
 (def (concrete_type type)
   (-> Type (Check [(List Nat) Type]))
-  (case type
+  (when type
     {.#UnivQ _}
     (do check.monad
       [[id var] check.var
@@ -232,9 +232,9 @@
       (Meta (List Instance)))
   (do ///.monad
     [compiler ///.compiler_state]
-    (case (|> alts
+    (when (|> alts
               (list#each (function (_ [alt_name alt_type])
-                           (case (check.result context
+                           (when (check.result context
                                                (do [! check.monad]
                                                  [[tvars alt_type] (concrete_type alt_type)
                                                   .let [[deps alt_type] (//.flat_function alt_type)]
@@ -256,7 +256,7 @@
 
 (def (provision sig_type compiler context dep)
   (-> Type Lux Type_Context Type (Check Instance))
-  (case (///.result compiler
+  (when (///.result compiler
                     (all ///.either
                          (do ///.monad [alts (..local_env sig_type)] (..candidate_provision (provision sig_type) context dep alts))
                          (do ///.monad [alts (..local_structs sig_type)] (..candidate_provision (provision sig_type) context dep alts))
@@ -265,7 +265,7 @@
     (check.failure error)
 
     {.#Right candidates}
-    (case candidates
+    (when candidates
       {.#End}
       (check.failure (format "No candidates for provisioning: " (%.type dep)))
 
@@ -281,9 +281,9 @@
   (do ///.monad
     [compiler ///.compiler_state
      context ///.type_context]
-    (case (|> alts
+    (when (|> alts
               (list#each (function (_ [alt_name alt_type])
-                           (case (<| (check.result context)
+                           (when (<| (check.result context)
                                      (do [! check.monad]
                                        [[tvars alt_type] (concrete_type alt_type)
                                         .let [[deps alt_type] (//.flat_function alt_type)]
@@ -315,7 +315,7 @@
 
 (def (var? input)
   (-> Code Bit)
-  (case input
+  (when input
     [_ {.#Symbol _}]
     #1
 
@@ -328,7 +328,7 @@
 
 (def (instance$ [constructor dependencies])
   (-> Instance Code)
-  (case dependencies
+  (when dependencies
     {.#End}
     (code.symbol constructor)
 
@@ -339,14 +339,14 @@
   (syntax (_ [member <code>.symbol
               args (<>.or (<>.and (<>.some <code>.symbol) <code>.end)
                           (<>.and (<>.some <code>.any) <code>.end))])
-    (case args
+    (when args
       {.#Left [args _]}
       (do [! ///.monad]
         [[member_idx sig_type] (..implicit_member member)
          input_types (monad.each ! ..implicit_type args)
          output_type ///.expected_type
          chosen_ones (alternatives sig_type member_idx input_types output_type)]
-        (case chosen_ones
+        (when chosen_ones
           {.#End}
           (///.failure (format "No implementation could be found for member: " (%.symbol member)))
 
diff --git a/stdlib/source/library/lux/meta/type/poly.lux b/stdlib/source/library/lux/meta/type/poly.lux
index a9a533d94..cccc9e518 100644
--- a/stdlib/source/library/lux/meta/type/poly.lux
+++ b/stdlib/source/library/lux/meta/type/poly.lux
@@ -33,7 +33,7 @@
         (in (.list (` (syntax ((, g!_) [(, g!type) <code>.any])
                         (do ///.monad
                           [(, g!type) (///.eval .Type (, g!type))]
-                          (case (is (.Either .Text .Code)
+                          (when (is (.Either .Text .Code)
                                     (<//>.result (<>.rec
                                                   (function ((, g!_) (, g!name))
                                                     (, body)))
@@ -46,7 +46,7 @@
 
 (def .public (code env type)
   (-> Env Type Code)
-  (case type
+  (when type
     {.#Primitive name params}
     (` {.#Primitive (, (code.text name))
                     (.list (,* (list#each (code env) params)))})
@@ -64,7 +64,7 @@
 
     {.#Apply {.#Primitive "" {.#End}}
              {.#Parameter idx}}
-    (case (<//>.argument env idx)
+    (when (<//>.argument env idx)
       0 (|> env (dictionary.value 0) maybe.trusted product.left (code env))
       idx (undefined))
     
diff --git a/stdlib/source/library/lux/meta/type/primitive.lux b/stdlib/source/library/lux/meta/type/primitive.lux
index ea277d239..8c6b0a98e 100644
--- a/stdlib/source/library/lux/meta/type/primitive.lux
+++ b/stdlib/source/library/lux/meta/type/primitive.lux
@@ -46,7 +46,7 @@
   [(def .public <name>
      (syntax (_ [[frame value] ..cast])
        (do meta.monad
-         [[name type_vars abstraction representation] (case frame
+         [[name type_vars abstraction representation] (when frame
                                                         {.#Some frame}
                                                         (..specific frame)
                                                         
diff --git a/stdlib/source/library/lux/meta/type/quotient.lux b/stdlib/source/library/lux/meta/type/quotient.lux
index 0687af5ce..04058c1e1 100644
--- a/stdlib/source/library/lux/meta/type/quotient.lux
+++ b/stdlib/source/library/lux/meta/type/quotient.lux
@@ -51,7 +51,7 @@
                          ...               (..Class (, g!t) (, g!c) (, g!%)))
                          ...             (, class))
                          ]
-                     (.case (.type_of (, class))
+                     (.when (.type_of (, class))
                        {.#Apply (, g!%) {.#Apply (, g!c) {.#Apply (, g!t) (, g!:quotient:)}}}
                        (.type_literal (..Quotient (, g!t) (, g!c) (, g!%)))
 
diff --git a/stdlib/source/library/lux/meta/type/refinement.lux b/stdlib/source/library/lux/meta/type/refinement.lux
index 5b7e939a5..fb7553897 100644
--- a/stdlib/source/library/lux/meta/type/refinement.lux
+++ b/stdlib/source/library/lux/meta/type/refinement.lux
@@ -55,12 +55,12 @@
 (def .public (only refiner values)
   (All (_ t %)
     (-> (Refiner t %) (List t) (List (Refined t %))))
-  (case values
+  (when values
     {.#End}
     {.#End}
 
     {.#Item head tail}
-    (case (refiner head)
+    (when (refiner head)
       {.#Some refined}
       {.#Item refined (only refiner tail)}
       
@@ -70,13 +70,13 @@
 (def .public (partition refiner values)
   (All (_ t %)
     (-> (Refiner t %) (List t) [(List (Refined t %)) (List t)]))
-  (case values
+  (when values
     {.#End}
     [{.#End} {.#End}]
 
     {.#Item head tail}
     (let [[yes no] (partition refiner tail)]
-      (case (refiner head)
+      (when (refiner head)
         {.#Some refined}
         [{.#Item refined yes}
          no]
@@ -93,7 +93,7 @@
                          ...               (..Refined (, g!t) (, g!%)))
                          ...             (, refiner))
                          ]
-                     (.case (.type_of (, refiner))
+                     (.when (.type_of (, refiner))
                        {.#Apply (, g!%) {.#Apply (, g!t) (, g!:refiner:)}}
                        (.type_literal (..Refined (, g!t) (, g!%)))
 
diff --git a/stdlib/source/library/lux/meta/type/resource.lux b/stdlib/source/library/lux/meta/type/resource.lux
index 3e652b8b9..7b1a83195 100644
--- a/stdlib/source/library/lux/meta/type/resource.lux
+++ b/stdlib/source/library/lux/meta/type/resource.lux
@@ -130,7 +130,7 @@
 (def .public exchange
   (syntax (_ [swaps ..indices])
     (macro.with_symbols [g!_ g!context g!!]
-      (case swaps
+      (when swaps
         {.#End}
         (in (list (` ..no_op)))
 
diff --git a/stdlib/source/library/lux/meta/version.lux b/stdlib/source/library/lux/meta/version.lux
index a1e00e3d4..af8da3bce 100644
--- a/stdlib/source/library/lux/meta/version.lux
+++ b/stdlib/source/library/lux/meta/version.lux
@@ -35,7 +35,7 @@
               default (<>.maybe <code>.any)])
     (do meta.monad
       [current meta.version]
-      (case (list#mix (function (_ [when then] choice)
+      (when (list#mix (function (_ [when then] choice)
                         (if (text#= when current)
                           {.#Some then}
                           choice))