diff --git a/.vscode/settings.json b/.vscode/settings.json
new file mode 100644
index 0000000..15ed943
--- /dev/null
+++ b/.vscode/settings.json
@@ -0,0 +1,5 @@
+{
+    "ocaml.sandbox": {
+        "kind": "global"
+    }
+}
\ No newline at end of file
diff --git a/bin/dune b/bin/dune
index cb42d58..3f429b4 100644
--- a/bin/dune
+++ b/bin/dune
@@ -1,4 +1,5 @@
 (executable
  (public_name poplpaper)
  (name main)
- (libraries poplpaper))
+ (libraries ppx_poplpaper)
+ (preprocess (pps ppx_poplpaper)))
diff --git a/dune-project b/dune-project
index c994249..2c5805c 100644
--- a/dune-project
+++ b/dune-project
@@ -1 +1,5 @@
 (lang dune 2.9)
+
+(name ppx_poplpaper)
+
+(generate_opam_files true)
\ No newline at end of file
diff --git a/flake.nix b/flake.nix
index fa27f8e..17cacf9 100644
--- a/flake.nix
+++ b/flake.nix
@@ -7,7 +7,11 @@
       in {
         devShell = pkgs.mkShell {
           inputsFrom = with flakePkgs; [ main ];
-          packages = with pkgs; [ ocamlPackages.ocaml-lsp ];
+          packages = (with pkgs; [ ]) ++ (with pkgs.ocamlPackages; [ocaml-lsp ppxlib
+          alcotest
+          yojson
+          ezjsonm
+          ]);
         };
       });
 }
diff --git a/lib/dune b/lib/dune
index a2fa703..40f1ec8 100644
--- a/lib/dune
+++ b/lib/dune
@@ -1,2 +1,6 @@
 (library
- (name poplpaper))
+ (name ppx_poplpaper)
+ (public_name ppx_poplpaper)
+ (kind ppx_rewriter)
+ (libraries ppxlib)
+ (preprocess (pps ppxlib.metaquot)))
diff --git a/lib/ppx_poplpaper.ml b/lib/ppx_poplpaper.ml
new file mode 100644
index 0000000..9867680
--- /dev/null
+++ b/lib/ppx_poplpaper.ml
@@ -0,0 +1,19 @@
+(* https://tarides.com/blog/2019-05-09-an-introduction-to-ocaml-ppx-ecosystem/ *)
+
+open Ppxlib
+
+let expand ~ctxt:_ (expr: expression) =
+  expr
+
+let ext = Extension.V3.declare
+  "monomorphic"
+  Extension.Context.expression
+  Ast_pattern.(single_expr_payload __)
+  expand
+
+let rule = Context_free.Rule.extension ext
+
+let () =
+  Driver.register_transformation
+    ~rules:[rule]
+    "monomorphic"
diff --git a/poplpaper.opam b/lib/ppx_poplpaper.mli
similarity index 100%
rename from poplpaper.opam
rename to lib/ppx_poplpaper.mli
diff --git a/ppx_poplpaper.opam b/ppx_poplpaper.opam
new file mode 100644
index 0000000..09ef829
--- /dev/null
+++ b/ppx_poplpaper.opam
@@ -0,0 +1,22 @@
+# This file is generated by dune, edit dune-project instead
+opam-version: "2.0"
+depends: [
+  "dune" {>= "2.9"}
+  "odoc" {with-doc}
+]
+build: [
+  ["dune" "subst"] {dev}
+  [
+    "dune"
+    "build"
+    "-p"
+    name
+    "-j"
+    jobs
+    "--promote-install-files=false"
+    "@install"
+    "@runtest" {with-test}
+    "@doc" {with-doc}
+  ]
+  ["dune" "install" "-p" name "--create-install-files" name]
+]
diff --git a/test/bin/dune b/test/bin/dune
new file mode 100644
index 0000000..142882a
--- /dev/null
+++ b/test/bin/dune
@@ -0,0 +1,4 @@
+(executable
+ (name pp)
+ (modules pp)
+ (libraries ppx_poplpaper ppxlib))
\ No newline at end of file
diff --git a/test/bin/pp.ml b/test/bin/pp.ml
new file mode 100644
index 0000000..4efb428
--- /dev/null
+++ b/test/bin/pp.ml
@@ -0,0 +1 @@
+Ppxlib.Driver.standalone ()
\ No newline at end of file
diff --git a/test/dune b/test/dune
index 6597498..8ba5a54 100644
--- a/test/dune
+++ b/test/dune
@@ -1,2 +1,13 @@
+(rule
+ (targets test.actual.ml)
+ (deps test.ml)
+ (action (run ./bin/pp.exe --impl %{deps} -o %{targets})))
+
+(rule
+ (alias runtest)
+ (action (diff test.expected.ml test.actual.ml)))
+
 (test
- (name poplpaper))
+ (name test)
+ (modules test)
+ (preprocess (pps ppx_poplpaper)))
\ No newline at end of file
diff --git a/test/poplpaper.ml b/test/test.expected.ml
similarity index 100%
rename from test/poplpaper.ml
rename to test/test.expected.ml
diff --git a/test/test.ml b/test/test.ml
new file mode 100644
index 0000000..e9f0a6e
--- /dev/null
+++ b/test/test.ml
@@ -0,0 +1,2 @@
+let%monomorphic prop0 (f : 'a -> 'b) (xs : 'a List.t) : bool =
+  List.length (List.map f xs) = 0