diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..69b2b33
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,38 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: actions/setup-node@v1
+        with:
+          node-version: "22"
+
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v12
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+
+      - name: Setup PureScript dependencies
+        run: npm i --global purescript@0.15.10 spago@next purescm@latest
+
+      - name: Build source
+        run: spago build
+
+      - name: Cache PureScript dependencies
+        uses: actions/cache@v2
+        with:
+          key: ${{ runner.os }}-spago-${{ hashFiles('**/spago.yaml') }}
+          path: |
+            .spago
+            output
+
+      - name: Run tests
+        run: |
+          nix-shell --run "purescm run --main Test.Chez.Main"
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..cf3485f
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,14 @@
+
+bower_components/
+node_modules/
+.pulp-cache/
+output/
+output-es/
+generated-docs/
+.psc-package/
+.psc*
+.purs*
+.psa*
+.spago
+.envrc
+.direnv
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..f081090
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,104 @@
+{
+  "nodes": {
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1696426674,
+        "narHash": "sha256-kvjfFW7WAETZlt09AgDn1MrtKzP7t90Vf7vypd3OL1U=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "flake-compat_2": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1696426674,
+        "narHash": "sha256-kvjfFW7WAETZlt09AgDn1MrtKzP7t90Vf7vypd3OL1U=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1720181791,
+        "narHash": "sha256-i4vJL12/AdyuQuviMMd1Hk2tsGt02hDNhA0Zj1m16N8=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "4284c2b73c8bce4b46a6adf23e16d9e2ec8da4bb",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "purescript-overlay": {
+      "inputs": {
+        "flake-compat": "flake-compat_2",
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "slimlock": "slimlock"
+      },
+      "locked": {
+        "lastModified": 1719849006,
+        "narHash": "sha256-0HpRwEdvAlbSka5tFLwokz2bEV+QgoGqRZ0BR/ghB6w=",
+        "owner": "thomashoneyman",
+        "repo": "purescript-overlay",
+        "rev": "6a00f4a8fbb42e0494a57c5da99b1375721a6c4b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "thomashoneyman",
+        "repo": "purescript-overlay",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "nixpkgs": "nixpkgs",
+        "purescript-overlay": "purescript-overlay"
+      }
+    },
+    "slimlock": {
+      "inputs": {
+        "nixpkgs": [
+          "purescript-overlay",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1688756706,
+        "narHash": "sha256-xzkkMv3neJJJ89zo3o2ojp7nFeaZc2G0fYwNXNJRFlo=",
+        "owner": "thomashoneyman",
+        "repo": "slimlock",
+        "rev": "cf72723f59e2340d24881fd7bf61cb113b4c407c",
+        "type": "github"
+      },
+      "original": {
+        "owner": "thomashoneyman",
+        "repo": "slimlock",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..135e36f
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,53 @@
+{
+  description = "PureScript core packages CI setup";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
+
+    flake-compat = {
+      url = "github:edolstra/flake-compat";
+      flake = false;
+    };
+
+    purescript-overlay.url = "github:thomashoneyman/purescript-overlay";
+    purescript-overlay.inputs.nixpkgs.follows = "nixpkgs";
+  };
+
+  outputs = { self, nixpkgs, ... }@inputs:
+    let
+      supportedSystems = [ "x86_64-linux" "x86_64-darwin" "aarch64-darwin" ];
+
+      forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
+
+      nixpkgsFor = forAllSystems (system: import nixpkgs {
+        inherit system;
+        overlays = builtins.attrValues self.overlays;
+      });
+    in
+    {
+      overlays = {
+        purescript = inputs.purescript-overlay.overlays.default;
+      };
+
+      devShells = forAllSystems (system:
+        let pkgs = nixpkgsFor.${system};
+            chez = pkgs.chez.overrideAttrs (final: prev: {
+              postFixup = if pkgs.stdenv.isDarwin then ''
+                install_name_tool -add_rpath ${pkgs.pcre2.out}/lib $out/bin/scheme
+              ''
+              else ''
+                patchelf $out/bin/scheme --add-rpath ${pkgs.pcre2.out}/lib
+              '';
+            });
+        in {
+          default = pkgs.mkShell {
+            name = "purescm";
+            packages = with pkgs; [
+              chez
+            ];
+          };
+        });
+
+      formatter = forAllSystems (system: nixpkgsFor.${system}.nixpkgs-fmt);
+    };
+}
diff --git a/shell.nix b/shell.nix
new file mode 100644
index 0000000..9d8d79e
--- /dev/null
+++ b/shell.nix
@@ -0,0 +1,13 @@
+# A compatibility file that allows non-flakes users to still get a development
+# shell with `nix-shell`.
+(import
+  (
+    let lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+    in fetchTarball {
+      url =
+        "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+      sha256 = lock.nodes.flake-compat.locked.narHash;
+    }
+  )
+  { src = ./.; }).shellNix
+
diff --git a/spago.lock b/spago.lock
new file mode 100644
index 0000000..66fb378
--- /dev/null
+++ b/spago.lock
@@ -0,0 +1,607 @@
+workspace:
+  packages:
+    chez-stdlib:
+      path: ./
+      dependencies:
+        - arrays
+        - console
+        - datetime
+        - effect
+        - foldable-traversable
+        - integers
+        - prelude
+        - refs
+        - unsafe-coerce
+      test_dependencies:
+        - assert
+      build_plan:
+        - arrays
+        - assert
+        - bifunctors
+        - console
+        - const
+        - contravariant
+        - control
+        - datetime
+        - distributive
+        - effect
+        - either
+        - enums
+        - exists
+        - foldable-traversable
+        - functions
+        - functors
+        - gen
+        - identity
+        - integers
+        - invariant
+        - lazy
+        - lists
+        - maybe
+        - newtype
+        - nonempty
+        - numbers
+        - ordered-collections
+        - orders
+        - partial
+        - prelude
+        - profunctor
+        - refs
+        - safe-coerce
+        - st
+        - tailrec
+        - tuples
+        - type-equality
+        - unfoldable
+        - unsafe-coerce
+  package_set:
+    address:
+      url: https://raw.githubusercontent.com/purescm/purescm/e891f4292630cae4d0ff1143a1594f600fc58512/package-sets/1.0.0.json
+    compiler: ">=0.15.10 <0.16.0"
+    content:
+      arrays:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: arrays
+      assert:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: assert
+      bifunctors: 6.0.0
+      catenable-lists: 7.0.0
+      console:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: console
+      const: 6.0.0
+      contravariant: 6.0.0
+      control:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: control
+      datetime:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: datetime
+      distributive: 6.0.0
+      effect:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: effect
+      either: 6.1.0
+      enums:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: enums
+      exceptions:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: exceptions
+      exists: 6.0.0
+      filterable: 5.0.0
+      foldable-traversable:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: foldable-traversable
+      foreign-object:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: foreign-object
+      free: 7.1.0
+      functions:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: functions
+        dependencies:
+          - prelude
+      functors: 5.0.0
+      gen: 4.0.0
+      identity: 6.0.0
+      integers:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: integers
+      invariant: 6.0.0
+      json:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: json
+      lazy:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: lazy
+      lcg: 4.0.0
+      lists:
+        git: https://github.com/purescm/purescript-lists.git
+        ref: 71502a132567cf7f32c2242d57b1cba2c77ebc15
+      maybe: 6.0.0
+      minibench:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: minibench
+      newtype: 5.0.0
+      nonempty: 7.0.0
+      numbers:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: numbers
+      ordered-collections: 3.1.1
+      orders: 6.0.0
+      parallel: 7.0.0
+      partial:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: partial
+        dependencies: []
+      prelude:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: prelude
+      profunctor: 6.0.0
+      quickcheck:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: quickcheck
+      random:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: random
+      record:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: record
+      refs:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: refs
+      safe-coerce: 2.0.0
+      semirings: 7.0.0
+      st:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: st
+      strings:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: strings
+      tailrec: 6.1.0
+      transformers: 6.0.0
+      tuples: 7.0.0
+      type-equality: 4.0.1
+      typelevel-prelude: 7.0.0
+      unfoldable:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: unfoldable
+      unsafe-coerce:
+        git: https://github.com/purescm/purescript-core.git
+        ref: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+        subdir: unsafe-coerce
+        dependencies: []
+      validation: 6.0.0
+  extra_packages: {}
+packages:
+  arrays:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: arrays
+    dependencies:
+      - bifunctors
+      - control
+      - foldable-traversable
+      - functions
+      - maybe
+      - nonempty
+      - partial
+      - prelude
+      - safe-coerce
+      - st
+      - tailrec
+      - tuples
+      - unfoldable
+      - unsafe-coerce
+  assert:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: assert
+    dependencies:
+      - console
+      - effect
+      - prelude
+  bifunctors:
+    type: registry
+    version: 6.0.0
+    integrity: sha256-/gZwC9YhNxZNQpnHa5BIYerCGM2jeX9ukZiEvYxm5Nw=
+    dependencies:
+      - const
+      - either
+      - newtype
+      - prelude
+      - tuples
+  console:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: console
+    dependencies:
+      - effect
+      - prelude
+  const:
+    type: registry
+    version: 6.0.0
+    integrity: sha256-tNrxDW8D8H4jdHE2HiPzpLy08zkzJMmGHdRqt5BQuTc=
+    dependencies:
+      - invariant
+      - newtype
+      - prelude
+  contravariant:
+    type: registry
+    version: 6.0.0
+    integrity: sha256-TP+ooAp3vvmdjfQsQJSichF5B4BPDHp3wAJoWchip6c=
+    dependencies:
+      - const
+      - either
+      - newtype
+      - prelude
+      - tuples
+  control:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: control
+    dependencies:
+      - newtype
+      - prelude
+  datetime:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: datetime
+    dependencies:
+      - bifunctors
+      - control
+      - either
+      - enums
+      - foldable-traversable
+      - functions
+      - gen
+      - integers
+      - lists
+      - maybe
+      - newtype
+      - numbers
+      - ordered-collections
+      - partial
+      - prelude
+      - tuples
+  distributive:
+    type: registry
+    version: 6.0.0
+    integrity: sha256-HTDdmEnzigMl+02SJB88j+gAXDx9VKsbvR4MJGDPbOQ=
+    dependencies:
+      - identity
+      - newtype
+      - prelude
+      - tuples
+      - type-equality
+  effect:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: effect
+    dependencies:
+      - prelude
+  either:
+    type: registry
+    version: 6.1.0
+    integrity: sha256-6hgTPisnMWVwQivOu2PKYcH8uqjEOOqDyaDQVUchTpY=
+    dependencies:
+      - control
+      - invariant
+      - maybe
+      - prelude
+  enums:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: enums
+    dependencies:
+      - control
+      - either
+      - gen
+      - maybe
+      - newtype
+      - nonempty
+      - partial
+      - prelude
+      - tuples
+      - unfoldable
+  exists:
+    type: registry
+    version: 6.0.0
+    integrity: sha256-A0JQHpTfo1dNOj9U5/Fd3xndlRSE0g2IQWOGor2yXn8=
+    dependencies:
+      - unsafe-coerce
+  foldable-traversable:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: foldable-traversable
+    dependencies:
+      - bifunctors
+      - const
+      - control
+      - either
+      - functors
+      - identity
+      - maybe
+      - newtype
+      - orders
+      - prelude
+      - tuples
+  functions:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: functions
+    dependencies:
+      - prelude
+  functors:
+    type: registry
+    version: 5.0.0
+    integrity: sha256-zfPWWYisbD84MqwpJSZFlvM6v86McM68ob8p9s27ywU=
+    dependencies:
+      - bifunctors
+      - const
+      - contravariant
+      - control
+      - distributive
+      - either
+      - invariant
+      - maybe
+      - newtype
+      - prelude
+      - profunctor
+      - tuples
+      - unsafe-coerce
+  gen:
+    type: registry
+    version: 4.0.0
+    integrity: sha256-f7yzAXWwr+xnaqEOcvyO3ezKdoes8+WXWdXIHDBCAPI=
+    dependencies:
+      - either
+      - foldable-traversable
+      - identity
+      - maybe
+      - newtype
+      - nonempty
+      - prelude
+      - tailrec
+      - tuples
+      - unfoldable
+  identity:
+    type: registry
+    version: 6.0.0
+    integrity: sha256-4wY0XZbAksjY6UAg99WkuKyJlQlWAfTi2ssadH0wVMY=
+    dependencies:
+      - control
+      - invariant
+      - newtype
+      - prelude
+  integers:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: integers
+    dependencies:
+      - maybe
+      - numbers
+      - prelude
+  invariant:
+    type: registry
+    version: 6.0.0
+    integrity: sha256-RGWWyYrz0Hs1KjPDA+87Kia67ZFBhfJ5lMGOMCEFoLo=
+    dependencies:
+      - control
+      - prelude
+  lazy:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: lazy
+    dependencies:
+      - control
+      - foldable-traversable
+      - invariant
+      - prelude
+  lists:
+    type: git
+    url: https://github.com/purescm/purescript-lists.git
+    rev: 71502a132567cf7f32c2242d57b1cba2c77ebc15
+    dependencies:
+      - bifunctors
+      - control
+      - foldable-traversable
+      - lazy
+      - maybe
+      - newtype
+      - nonempty
+      - partial
+      - prelude
+      - tailrec
+      - tuples
+      - unfoldable
+  maybe:
+    type: registry
+    version: 6.0.0
+    integrity: sha256-5cCIb0wPwbat2PRkQhUeZO0jcAmf8jCt2qE0wbC3v2Q=
+    dependencies:
+      - control
+      - invariant
+      - newtype
+      - prelude
+  newtype:
+    type: registry
+    version: 5.0.0
+    integrity: sha256-gdrQu8oGe9eZE6L3wOI8ql/igOg+zEGB5ITh2g+uttw=
+    dependencies:
+      - prelude
+      - safe-coerce
+  nonempty:
+    type: registry
+    version: 7.0.0
+    integrity: sha256-54ablJZUHGvvlTJzi3oXyPCuvY6zsrWJuH/dMJ/MFLs=
+    dependencies:
+      - control
+      - foldable-traversable
+      - maybe
+      - prelude
+      - tuples
+      - unfoldable
+  numbers:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: numbers
+    dependencies:
+      - functions
+      - maybe
+      - prelude
+  ordered-collections:
+    type: registry
+    version: 3.1.1
+    integrity: sha256-boSYHmlz4aSbwsNN4VxiwCStc0t+y1F7BXmBS+1JNtI=
+    dependencies:
+      - arrays
+      - foldable-traversable
+      - gen
+      - lists
+      - maybe
+      - partial
+      - prelude
+      - st
+      - tailrec
+      - tuples
+      - unfoldable
+  orders:
+    type: registry
+    version: 6.0.0
+    integrity: sha256-nBA0g3/ai0euH8q9pSbGqk53W2q6agm/dECZTHcoink=
+    dependencies:
+      - newtype
+      - prelude
+  partial:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: partial
+    dependencies: []
+  prelude:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: prelude
+    dependencies: []
+  profunctor:
+    type: registry
+    version: 6.0.0
+    integrity: sha256-99NzxFgTr4CGlCSRYG1kShL+JhYbihhHtbOk1/0R5zI=
+    dependencies:
+      - control
+      - distributive
+      - either
+      - exists
+      - invariant
+      - newtype
+      - prelude
+      - tuples
+  refs:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: refs
+    dependencies:
+      - effect
+      - prelude
+  safe-coerce:
+    type: registry
+    version: 2.0.0
+    integrity: sha256-a1ibQkiUcbODbLE/WAq7Ttbbh9ex+x33VCQ7GngKudU=
+    dependencies:
+      - unsafe-coerce
+  st:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: st
+    dependencies:
+      - effect
+      - partial
+      - prelude
+      - tailrec
+      - unsafe-coerce
+  tailrec:
+    type: registry
+    version: 6.1.0
+    integrity: sha256-Xx19ECVDRrDWpz9D2GxQHHV89vd61dnXxQm0IcYQHGk=
+    dependencies:
+      - bifunctors
+      - effect
+      - either
+      - identity
+      - maybe
+      - partial
+      - prelude
+      - refs
+  tuples:
+    type: registry
+    version: 7.0.0
+    integrity: sha256-1rXgTomes9105BjgXqIw0FL6Fz1lqqUTLWOumhWec1M=
+    dependencies:
+      - control
+      - invariant
+      - prelude
+  type-equality:
+    type: registry
+    version: 4.0.1
+    integrity: sha256-Hs9D6Y71zFi/b+qu5NSbuadUQXe5iv5iWx0226vOHUw=
+    dependencies: []
+  unfoldable:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: unfoldable
+    dependencies:
+      - foldable-traversable
+      - maybe
+      - partial
+      - prelude
+      - tuples
+  unsafe-coerce:
+    type: git
+    url: https://github.com/purescm/purescript-core.git
+    rev: 98f12cc76d4941f979f2530da94f5b46ce9551cd
+    subdir: unsafe-coerce
+    dependencies: []
diff --git a/spago.yaml b/spago.yaml
new file mode 100644
index 0000000..7606378
--- /dev/null
+++ b/spago.yaml
@@ -0,0 +1,24 @@
+package:
+  name: chez-stdlib
+  dependencies:
+    - arrays
+    - console
+    - datetime
+    - effect
+    - foldable-traversable
+    - integers
+    - prelude
+    - refs
+    - unsafe-coerce
+  test:
+    main: Test.Chez.Main
+    dependencies:
+      - assert
+workspace:
+  backend:
+    cmd: purescm
+    args:
+      - build
+  packageSet:
+    url: https://raw.githubusercontent.com/purescm/purescm/e891f4292630cae4d0ff1143a1594f600fc58512/package-sets/1.0.0.json
+  extraPackages: {}
diff --git a/src/Chez/Thread.purs b/src/Chez/Thread.purs
new file mode 100644
index 0000000..f8b4280
--- /dev/null
+++ b/src/Chez/Thread.purs
@@ -0,0 +1,90 @@
+-- | This module provides a simple interface to the Chez Scheme thread API.
+-- | See Chapter 15 of the Chez Scheme User's Guide for more information:
+-- | https://cisco.github.io/ChezScheme/csug10.0/threads.html
+module Chez.Thread
+  ( Thread
+  , ThreadId
+  , Mutex
+  , Condition
+  , fork
+  , join
+  , threadIdToInt
+  , makeMutex
+  , withMutex
+  , makeCondition
+  , conditionWait
+  , conditionSignal
+  , sleep
+  ) where
+
+import Prelude
+
+import Data.Int as Int
+import Data.Time.Duration (class Duration, Milliseconds(..))
+import Data.Time.Duration as Duration
+import Effect (Effect)
+import Effect.Uncurried (EffectFn1, EffectFn2)
+import Effect.Uncurried as Uncurried
+import Unsafe.Coerce (unsafeCoerce)
+
+--------------------------------------------------------------------------------
+-- Thread creation/termination
+
+foreign import data ThreadId :: Type
+
+threadIdToInt :: ThreadId -> Int
+threadIdToInt = unsafeCoerce
+
+foreign import data Thread :: Type
+
+foreign import forkThreadImpl :: EffectFn1 (EffectFn1 ThreadId Unit) Thread
+
+fork :: (ThreadId -> Effect Unit) -> Effect Thread
+fork fn = Uncurried.runEffectFn1 forkThreadImpl (Uncurried.mkEffectFn1 fn)
+
+foreign import joinThreadImpl :: EffectFn1 Thread Unit
+
+join :: Thread -> Effect Unit
+join = Uncurried.runEffectFn1 joinThreadImpl
+
+--------------------------------------------------------------------------------
+-- Thread syncronisation - mutexes
+
+data Mutex
+
+foreign import makeMutex :: Effect Mutex
+
+foreign import withMutexImpl :: EffectFn2 Mutex (Effect Unit) Unit
+
+withMutex :: Mutex -> Effect Unit -> Effect Unit
+withMutex mutex fn = Uncurried.runEffectFn2 withMutexImpl mutex fn
+
+--------------------------------------------------------------------------------
+-- Thread syncronisation - conditions (aka semaphores)
+
+data Condition
+
+foreign import makeCondition :: Effect Condition
+
+foreign import conditionWaitImpl :: EffectFn2 Condition Mutex Unit
+
+conditionWait :: Condition -> Mutex -> Effect Unit
+conditionWait condition mutex = Uncurried.runEffectFn2 conditionWaitImpl condition mutex
+
+foreign import conditionSignalImpl :: EffectFn1 Condition Unit
+
+conditionSignal :: Condition -> Effect Unit
+conditionSignal condition = Uncurried.runEffectFn1 conditionSignalImpl condition
+
+--------------------------------------------------------------------------------
+-- Thread sleep
+
+foreign import sleepImpl :: EffectFn2 Int Int Unit
+
+sleep :: forall a. Duration a => a -> Effect Unit
+sleep duration = do
+  let
+    (Milliseconds millis) = Duration.fromDuration duration
+    seconds = Int.floor (millis / 1000.0)
+    nanoseconds = Int.floor ((millis - Int.toNumber (seconds * 1000)) * 1000000.0)
+  Uncurried.runEffectFn2 sleepImpl nanoseconds seconds
diff --git a/src/Chez/Thread.ss b/src/Chez/Thread.ss
new file mode 100644
index 0000000..c1d0dba
--- /dev/null
+++ b/src/Chez/Thread.ss
@@ -0,0 +1,36 @@
+(library (Chez.Thread foreign)
+  (export
+    forkThreadImpl
+    joinThreadImpl
+    makeMutex
+    withMutexImpl
+    mutexNameImpl
+    makeCondition
+    conditionWaitImpl
+    conditionSignalImpl
+    sleepImpl)
+  (import (chezscheme))
+
+  (define forkThreadImpl
+    (lambda (threadFn)
+      (fork-thread
+        (lambda ()
+          (threadFn (get-thread-id))))))
+
+  (define joinThreadImpl (lambda (thread) (thread-join thread)))
+
+  (define makeMutex (lambda () (make-mutex)))
+
+  (define withMutexImpl (lambda (mutex thunk) (with-mutex mutex (thunk))))
+
+  (define mutexNameImpl (lambda (mutex) (mutex-name mutex)))
+
+  (define makeCondition (lambda () (make-condition)))
+
+  (define conditionWaitImpl (lambda (condition mutex) (condition-wait condition mutex)))
+
+  (define conditionSignalImpl (lambda (condition) (condition-signal condition)))
+
+  ;; TODO: make-time shoud probably be in a Chez.Time module
+  (define sleepImpl (lambda (nanoseconds seconds) (sleep (make-time 'time-duration nanoseconds seconds))))
+  )
diff --git a/test/Test/Main.purs b/test/Test/Main.purs
new file mode 100644
index 0000000..221ab1a
--- /dev/null
+++ b/test/Test/Main.purs
@@ -0,0 +1,35 @@
+module Test.Chez.Main where
+
+import Prelude
+
+import Chez.Thread as Thread
+import Data.Array as Array
+import Data.Time.Duration (Milliseconds(..))
+import Data.Traversable (for, for_)
+import Effect (Effect)
+import Effect.Ref as Ref
+import Effect.Unsafe (unsafePerformEffect)
+import Test.Assert (assertEqual)
+
+main :: Effect Unit
+main = do
+  counter <- Ref.new 0
+
+  let
+    modifyFn :: Int -> Int
+    modifyFn x = unsafePerformEffect do
+      Thread.sleep (Milliseconds 10.0)
+      pure (x + 1)
+
+    threadFn _threadId = do
+      for_ (Array.range 0 9) \_ -> do
+        newCounter <- Ref.modify modifyFn counter
+        -- log $ "Thread " <> show (Thread.threadIdToInt threadId) <> ": new counter is " <> show newCounter
+        pure newCounter
+
+  threads <- for (Array.range 0 9) \_ -> Thread.fork threadFn
+
+  for_ threads Thread.join
+
+  finalCount <- Ref.read counter
+  assertEqual { actual: finalCount, expected: 100 }