diff --git a/src/wip/cache/cache.pysty3 b/src/wip/cache/cache.pysty3
new file mode 100644
index 0000000..6337939
--- /dev/null
+++ b/src/wip/cache/cache.pysty3
@@ -0,0 +1,121 @@
+__HEADER__(Cache definitions of previous LaTeX runs to avoid computations)
+
+
+
+%%%% This is just a proof of concept package,
+%%%% there is possibly more room for clean-up
+%%%% and / or speed-up etc.
+
+%%% Also, the provided 
+%%% \DeclareCachedDocumentCommand
+%%% is of course not really
+%%% useful and just for demonstration
+%%% purposes
+
+\bool_new:N \g__cache_cache_bool
+\int_new:N \g__cache_cache_version_document_int
+\int_new:N \g__cache_cache_version_aux_int
+\int_gset:Nn \g__cache_cache_version_aux_int { -1 }
+
+\tl_new:N \g__cache_dump_auxfile_tl
+\tl_new:N \g__cache_lazy_document_tl
+\tl_new:N \g__cache_lazy_auxfile_tl
+
+\keys_define:nn { cache }
+  {
+    cache              .bool_set:N    = \g__cache_cache_bool,
+    cache              .default:n     = { true },
+    __cache version__  .int_set:N     = \g__cache_cache_version_document_int,
+    cache version      .meta:nn       = { cache } { cache = true, __cache version__ = #1 },
+    cache version      .default:n     = { 0 },
+  }
+\RequirePackage{l3keys2e}
+\ProcessKeysOptions{cache}
+
+
+% Setting up lazy execution and
+% selecting of executing after reading of aux file
+% if cache option has been used
+\bool_if:NTF \g__cache_cache_bool
+  {
+    %% Writing things (at one go) to aux file at end of document:
+    \cs_new:Npn \__cache_put_aux:n #1 
+      {
+        \tl_gput_right:Nn \g__cache_dump_auxfile_tl { #1 }
+      }
+    \cs_generate_variant:Nn \__cache_put_aux:n { x, V }
+
+    \cs_generate_variant:Nn \iow_now:Nn { c V }
+
+    %%% Handles dumping data to aux file at end of document
+    \hook_gput_code:nnn { enddocument } { cache }
+      {
+        \iow_now:cV { @auxout } \g__cache_dump_auxfile_tl
+      }
+
+    %%% Writes the current cache version into aux file
+    \__cache_put_aux:x
+      {
+        \ExplSyntaxOn
+        \int_gset:Nn \exp_not:N \g__cache_cache_version_aux_int
+          {
+            \int_use:N \g__cache_cache_version_document_int
+          }
+        \ExplSyntaxOff
+      }
+
+    %%% Executing something lazily at beginning of document
+    %%% Lazy code only gets executed if auxfile version is older than document
+    \cs_new:Npn \__cache_lazy:n
+      {
+        \tl_gput_right:Nn \g__cache_lazy_document_tl 
+      }
+
+    %%% Caching things. Handles writing and reading to aux file
+    %%% and makes code available in the next run of LaTeX
+    \cs_new:Npn \__cache_cache:n #1
+      {
+        \tl_set:Nn \l_tmpa_tl
+          {
+            \csname tl_gput_right:cn \endcsname { g__cache_lazy_auxfile_tl } { #1 }
+          }
+        \regex_replace_all:nnN { \cP\# } { \cO\# } \l_tmpa_tl
+        \__cache_put_aux:V \l_tmpa_tl
+      }
+
+    %%% This handles loading either the cached definitions
+    %%% from last run or executing the lazy definitions from the current run
+    %%% after loading the aux file
+    \hook_gput_code:nnn { begindocument } { cache }
+      {
+        \int_compare:nNnTF
+          \g__cache_cache_version_aux_int < \g__cache_cache_version_document_int
+            {
+              \tl_use:N \g__cache_lazy_document_tl
+            }
+            {
+              \tl_use:N \g__cache_lazy_auxfile_tl
+            }
+      }
+  }
+  {
+    \cs_set_eq:NN \__cache_lazy:n \use:n
+    \cs_set_eq:NN \__cache_cache:n \use_none:n
+  }
+
+\cs_new:Npn \__cached_new_document_command:nnn #1 #2 #3
+  {
+    \NewDocumentCommand{#1}{#2}{#3}
+    \__cache_cache:n
+      {
+        \csname __cached_new_document_command:nnn \endcsname { #1 } { #2 } { #3 }
+      }
+  }
+
+\NewDocumentCommand{\DeclareCachedDocumentCommand}{mmm}
+  {
+    \__cache_lazy:n
+      {
+        \__cached_new_document_command:nnn{#1}{#2}{#3}
+      }
+  }
diff --git a/tests/wip/cache/test.tex b/tests/wip/cache/test.tex
new file mode 100644
index 0000000..eb85da9
--- /dev/null
+++ b/tests/wip/cache/test.tex
@@ -0,0 +1,43 @@
+\documentclass{article}
+
+
+
+%%% Setting a higher cache version will cause a re-evaluation of the
+% \DeclareCachedDocumentCommand macros present in the preamble
+% Otherwise, the definitions can be altered or even removed without breaking
+% the document, as long as the aux file is present.
+
+
+
+%% \DeclareCachedDocumentCommand is now just a plain wrapper around \DeclareDocumentCommand
+%% that implements this caching, so it is not useful on itself
+%% 
+%% If \DeclareCachedDocumentCommand is, however, some macro that does lengthy computations
+%% and then issues one ore more of underlying \DeclareDocumentCommands
+%% we can save this computation on the second run, since we do not evaluate
+%% \DeclareCachedDocumentCommand further (we just copied its definition)
+%% and load the plain definitions that the  invocation produced in the last run
+%% and that we saved to the aux file for restoration.
+
+\usepackage[cache version = 0]{mkessler-cache}
+
+\DeclareCachedDocumentCommand\foo{m}{foo: Called with argument '#1'. hi}
+\DeclareCachedDocumentCommand\baz{m}{baz: Called with argument '#1'.}
+
+\DeclareCachedDocumentCommand\parser{!s !t+}
+  {
+    \IfBooleanT {#1} {*}
+    \IfBooleanT {#2} {$\dagger$}
+  }
+
+\begin{document}
+
+\foo {  one  }
+
+\baz{ arg }
+
+\parser*+
+
+Some text.
+  
+\end{document}