diff --git a/crates/aiken-lang/src/expr.rs b/crates/aiken-lang/src/expr.rs
index 976c47df..1fdea112 100644
--- a/crates/aiken-lang/src/expr.rs
+++ b/crates/aiken-lang/src/expr.rs
@@ -1,4 +1,5 @@
 use std::{collections::HashMap, rc::Rc};
+use uplc::KeyValuePairs;
 
 use vec1::Vec1;
 
@@ -607,32 +608,38 @@ impl UntypedExpr {
                 preferred_format: ByteArrayFormatPreference::HexadecimalString,
             }),
             PlutusData::Array(args) => {
-                let inner;
                 match tipo {
                     Type::App {
-                        module, name, args, ..
+                        module,
+                        name,
+                        args: type_args,
+                        ..
                     } if module.is_empty() && name.as_str() == "List" => {
-                        if let [arg] = &args[..] {
-                            inner = arg.clone()
+                        if let [inner] = &type_args[..] {
+                            Ok(UntypedExpr::List {
+                                location: Span::empty(),
+                                elements: args
+                                    .into_iter()
+                                    .map(|arg| UntypedExpr::reify(data_types, arg, inner))
+                                    .collect::<Result<Vec<_>, _>>()?,
+                                tail: None,
+                            })
                         } else {
-                            return Err("invalid List type annotation: the list has multiple type-parameters.".to_string());
-                        };
-                    }
-                    _ => {
-                        return Err(format!(
-                            "invalid type annotation. expected List but got: {tipo:?}"
-                        ))
+                            Err("invalid List type annotation: the list has multiple type-parameters.".to_string())
+                        }
                     }
+                    Type::Tuple { elems } => Ok(UntypedExpr::Tuple {
+                        location: Span::empty(),
+                        elems: args
+                            .into_iter()
+                            .zip(elems)
+                            .map(|(arg, arg_type)| UntypedExpr::reify(data_types, arg, arg_type))
+                            .collect::<Result<Vec<_>, _>>()?,
+                    }),
+                    _ => Err(format!(
+                        "invalid type annotation. expected List but got: {tipo:?}"
+                    )),
                 }
-
-                Ok(UntypedExpr::List {
-                    location: Span::empty(),
-                    elements: args
-                        .into_iter()
-                        .map(|arg| UntypedExpr::reify(data_types, arg, &inner))
-                        .collect::<Result<Vec<_>, _>>()?,
-                    tail: None,
-                })
             }
 
             PlutusData::Constr(Constr {
@@ -716,7 +723,22 @@ impl UntypedExpr {
                 ))
             }
 
-            PlutusData::Map(..) => todo!("reify Map"),
+            PlutusData::Map(indef_or_def) => {
+                let kvs = match indef_or_def {
+                    KeyValuePairs::Def(kvs) => kvs,
+                    KeyValuePairs::Indef(kvs) => kvs,
+                };
+
+                UntypedExpr::reify(
+                    data_types,
+                    PlutusData::Array(
+                        kvs.into_iter()
+                            .map(|(k, v)| PlutusData::Array(vec![k, v]))
+                            .collect(),
+                    ),
+                    tipo,
+                )
+            }
         }
     }
 
diff --git a/crates/aiken-lang/src/gen_uplc.rs b/crates/aiken-lang/src/gen_uplc.rs
index 59182f88..c1eb90c5 100644
--- a/crates/aiken-lang/src/gen_uplc.rs
+++ b/crates/aiken-lang/src/gen_uplc.rs
@@ -75,6 +75,10 @@ pub struct CodeGenerator<'a> {
 }
 
 impl<'a> CodeGenerator<'a> {
+    pub fn data_types(&self) -> &IndexMap<DataTypeKey, &'a TypedDataType> {
+        &self.data_types
+    }
+
     pub fn new(
         functions: IndexMap<FunctionAccessKey, &'a TypedFunction>,
         data_types: IndexMap<DataTypeKey, &'a TypedDataType>,
diff --git a/crates/aiken-lang/src/tipo.rs b/crates/aiken-lang/src/tipo.rs
index 0f180ea5..c1ee9711 100644
--- a/crates/aiken-lang/src/tipo.rs
+++ b/crates/aiken-lang/src/tipo.rs
@@ -57,6 +57,18 @@ pub enum Type {
 }
 
 impl Type {
+    pub fn qualifier(&self) -> Option<(String, String)> {
+        match self {
+            Type::App { module, name, .. } => Some((module.to_string(), name.to_string())),
+            Type::Fn { .. } => None,
+            Type::Var { ref tipo } => match &*tipo.borrow() {
+                TypeVar::Link { ref tipo } => tipo.qualifier(),
+                _ => None,
+            },
+            Type::Tuple { .. } => Some((String::new(), "Tuple".to_string())),
+        }
+    }
+
     pub fn is_result_constructor(&self) -> bool {
         match self {
             Type::Fn { ret, .. } => ret.is_result(),
diff --git a/crates/aiken-project/src/lib.rs b/crates/aiken-project/src/lib.rs
index 349ff7d6..8849a091 100644
--- a/crates/aiken-project/src/lib.rs
+++ b/crates/aiken-project/src/lib.rs
@@ -34,6 +34,7 @@ use aiken_lang::{
     },
     builtins,
     expr::{TypedExpr, UntypedExpr},
+    gen_uplc::builder::convert_opaque_type,
     tipo::{Type, TypeInfo},
     IdGenerator,
 };
@@ -46,7 +47,7 @@ use pallas::ledger::{
     primitives::babbage::{self as cardano, PolicyId},
     traverse::ComputeHash,
 };
-use script::{Assertion, Test, TestResult};
+use script::{Assertion, Fuzzer, Test, TestResult};
 use std::{
     collections::HashMap,
     fs::{self, File},
@@ -844,7 +845,7 @@ where
 
                 let via = parameter.via.clone();
 
-                let type_info = parameter.tipo.clone();
+                let type_info = convert_opaque_type(&parameter.tipo, generator.data_types());
 
                 let body = TypedExpr::Fn {
                     location: Span::empty(),
@@ -876,7 +877,10 @@ where
                     name.to_string(),
                     *can_error,
                     program,
-                    (fuzzer, type_info),
+                    Fuzzer {
+                        program: fuzzer,
+                        type_info,
+                    },
                 );
 
                 programs.push(prop);
diff --git a/crates/aiken-project/src/script.rs b/crates/aiken-project/src/script.rs
index 256929a3..ff297682 100644
--- a/crates/aiken-project/src/script.rs
+++ b/crates/aiken-project/src/script.rs
@@ -73,7 +73,7 @@ impl Test {
         name: String,
         can_error: bool,
         program: Program<NamedDeBruijn>,
-        fuzzer: (Program<NamedDeBruijn>, Rc<Type>),
+        fuzzer: Fuzzer<NamedDeBruijn>,
     ) -> Test {
         Test::PropertyTest(PropertyTest {
             input_path,
@@ -130,11 +130,17 @@ pub struct PropertyTest {
     pub name: String,
     pub can_error: bool,
     pub program: Program<NamedDeBruijn>,
-    pub fuzzer: (Program<NamedDeBruijn>, Rc<Type>),
+    pub fuzzer: Fuzzer<NamedDeBruijn>,
 }
 
 unsafe impl Send for PropertyTest {}
 
+#[derive(Debug, Clone)]
+pub struct Fuzzer<T> {
+    pub program: Program<T>,
+    pub type_info: Rc<Type>,
+}
+
 impl PropertyTest {
     const MAX_TEST_RUN: usize = 100;
 
@@ -177,7 +183,7 @@ impl PropertyTest {
 
     fn run_once(&self, seed: u32) -> (u32, Option<PlutusData>) {
         let (next_prng, value) = Prng::from_seed(seed)
-            .sample(&self.fuzzer.0)
+            .sample(&self.fuzzer.program)
             .expect("running seeded Prng cannot fail.");
 
         let result = self.eval(&value);
@@ -207,7 +213,7 @@ impl PropertyTest {
     }
 
     pub fn eval(&self, value: &PlutusData) -> EvalResult {
-        let term = convert_data_to_type(Term::data(value.clone()), &self.fuzzer.1)
+        let term = convert_data_to_type(Term::data(value.clone()), &self.fuzzer.type_info)
             .try_into()
             .expect("safe conversion from Name -> NamedDeBruijn");
         self.program.apply_term(&term).eval(ExBudget::max())
@@ -399,7 +405,7 @@ impl<'a> Counterexample<'a> {
         // test cases many times. Given that tests are fully deterministic, we can
         // memoize the already seen choices to avoid re-running the generators and
         // the test (which can be quite expensive).
-        match Prng::from_choices(choices).sample(&self.property.fuzzer.0) {
+        match Prng::from_choices(choices).sample(&self.property.fuzzer.program) {
             // Shrinked choices led to an impossible generation.
             None => false,
 
@@ -653,7 +659,7 @@ impl PropertyTestResult<PlutusData> {
             counterexample: match self.counterexample {
                 None => None,
                 Some(counterexample) => Some(
-                    UntypedExpr::reify(data_types, counterexample, &self.test.fuzzer.1)
+                    UntypedExpr::reify(data_types, counterexample, &self.test.fuzzer.type_info)
                         .expect("Failed to reify counterexample?"),
                 ),
             },
diff --git a/examples/acceptance_tests/095/aiken.lock b/examples/acceptance_tests/095/aiken.lock
index 6e350cda..17a9c623 100644
--- a/examples/acceptance_tests/095/aiken.lock
+++ b/examples/acceptance_tests/095/aiken.lock
@@ -1,7 +1,16 @@
 # This file was generated by Aiken
 # You typically do not need to edit this file
 
+[[requirements]]
+name = "aiken-lang/stdlib"
+version = "main"
+source = "github"
+
+[[packages]]
+name = "aiken-lang/stdlib"
+version = "main"
 requirements = []
-packages = []
+source = "github"
 
 [etags]
+"aiken-lang/stdlib@main" = [{ secs_since_epoch = 1709304545, nanos_since_epoch = 842241000 }, "cf946239d3dd481ed41f20e56bf24910b5229ea35aa171a708edc2a47fc20a7b"]
diff --git a/examples/acceptance_tests/095/aiken.toml b/examples/acceptance_tests/095/aiken.toml
index 92735c12..0020ed78 100644
--- a/examples/acceptance_tests/095/aiken.toml
+++ b/examples/acceptance_tests/095/aiken.toml
@@ -1,3 +1,8 @@
 name = "aiken-lang/acceptance_test_095"
 version = "0.0.0"
 description = ""
+
+[[dependencies]]
+name = "aiken-lang/stdlib"
+version = "main"
+source = "github"
diff --git a/examples/acceptance_tests/095/lib/aiken/fuzz.ak b/examples/acceptance_tests/095/lib/aiken/fuzz.ak
new file mode 100644
index 00000000..be0f647a
--- /dev/null
+++ b/examples/acceptance_tests/095/lib/aiken/fuzz.ak
@@ -0,0 +1,130 @@
+use aiken/builtin
+
+const max_int: Int = 255
+
+pub type PRNG {
+  Seeded { seed: Int, choices: List<Int> }
+  Replayed { choices: List<Int> }
+}
+
+pub type Fuzzer<a> =
+  fn(PRNG) -> Option<(PRNG, a)>
+
+// Primitives
+
+pub fn any_int() -> Fuzzer<Int> {
+  fn(prng: PRNG) -> Option<(PRNG, Int)> {
+    when prng is {
+      Seeded { seed, choices } -> {
+        let digest =
+          seed
+            |> builtin.integer_to_bytearray(True, 32, _)
+            |> builtin.blake2b_256()
+
+        let choice =
+          digest
+            |> builtin.index_bytearray(0)
+
+        let new_seed =
+          digest
+            |> builtin.slice_bytearray(1, 4, _)
+            |> builtin.bytearray_to_integer(True, _)
+
+        Some((Seeded { seed: new_seed, choices: [choice, ..choices] }, choice))
+      }
+
+      Replayed { choices } ->
+        when choices is {
+          [] -> None
+          [head, ..tail] ->
+            if head >= 0 && head <= max_int {
+              Some((Replayed { choices: tail }, head))
+            } else {
+              None
+            }
+        }
+    }
+  }
+}
+
+pub fn constant(a: a) -> Fuzzer<a> {
+  fn(s0) { Some((s0, a)) }
+}
+
+pub fn and_then(fuzz_a: Fuzzer<a>, f: fn(a) -> Fuzzer<b>) -> Fuzzer<b> {
+  fn(s0) {
+    when fuzz_a(s0) is {
+      Some((s1, a)) -> f(a)(s1)
+      None -> None
+    }
+  }
+}
+
+pub fn map(fuzz_a: Fuzzer<a>, f: fn(a) -> b) -> Fuzzer<b> {
+  fn(s0) {
+    when fuzz_a(s0) is {
+      Some((s1, a)) -> Some((s1, f(a)))
+      None -> None
+    }
+  }
+}
+
+pub fn map2(fuzz_a: Fuzzer<a>, fuzz_b: Fuzzer<b>, f: fn(a, b) -> c) -> Fuzzer<c> {
+  fn(s0) {
+    when fuzz_a(s0) is {
+      Some((s1, a)) ->
+        when fuzz_b(s1) is {
+          Some((s2, b)) -> Some((s2, f(a, b)))
+          None -> None
+        }
+      None -> None
+    }
+  }
+}
+
+pub fn map4(
+  fuzz_a: Fuzzer<a>,
+  fuzz_b: Fuzzer<b>,
+  fuzz_c: Fuzzer<c>,
+  fuzz_d: Fuzzer<d>,
+  f: fn(a, b, c, d) -> result,
+) -> Fuzzer<result> {
+  fn(s0) {
+    when fuzz_a(s0) is {
+      Some((s1, a)) ->
+        when fuzz_b(s1) is {
+          Some((s2, b)) ->
+            when fuzz_c(s2) is {
+              Some((s3, c)) ->
+                when fuzz_d(s3) is {
+                  Some((s4, d)) -> Some((s4, f(a, b, c, d)))
+                  None -> None
+                }
+              None -> None
+            }
+          None -> None
+        }
+
+      None -> None
+    }
+  }
+}
+
+// Builders
+
+fn any_bool() -> Fuzzer<Bool> {
+  any_int() |> map(fn(n) { n <= 127 })
+}
+
+fn any_list(fuzz_a: Fuzzer<a>) -> Fuzzer<List<a>> {
+  any_bool()
+    |> and_then(
+         fn(continue) {
+           if continue {
+             map2(fuzz_a, any_list(fuzz_a), fn(head, tail) { [head, ..tail] })
+           } else {
+             constant([])
+           }
+         },
+       )
+}
diff --git a/examples/acceptance_tests/095/lib/foo.ak b/examples/acceptance_tests/095/lib/foo.ak
index 66a2b591..b73ea8d8 100644
--- a/examples/acceptance_tests/095/lib/foo.ak
+++ b/examples/acceptance_tests/095/lib/foo.ak
@@ -1,166 +1,47 @@
-use aiken/builtin
-
-const max_int: Int = 255
-
-pub type PRNG {
-  Seeded { seed: Int, choices: List<Int> }
-  Replayed { choices: List<Int> }
-}
-
-type Fuzzer<a> =
-  fn(PRNG) -> Option<(PRNG, a)>
-
-// Primitives
-
-fn any_int(prng: PRNG) -> Option<(PRNG, Int)> {
-  when prng is {
-    Seeded { seed, choices } -> {
-      let digest =
-        seed
-          |> builtin.integer_to_bytearray(True, 32, _)
-          |> builtin.blake2b_256()
-
-      let choice =
-        digest
-          |> builtin.index_bytearray(0)
-
-      let new_seed =
-        digest
-          |> builtin.slice_bytearray(1, 4, _)
-          |> builtin.bytearray_to_integer(True, _)
-
-      Some((Seeded { seed: new_seed, choices: [choice, ..choices] }, choice))
-    }
-
-    Replayed { choices } ->
-      when choices is {
-        [] -> None
-        [head, ..tail] ->
-          if head >= 0 && head <= max_int {
-            Some((Replayed { choices: tail }, head))
-          } else {
-            None
-          }
-      }
-  }
-}
-
-pub fn constant(a: a) -> Fuzzer<a> {
-  fn(s0) { Some((s0, a)) }
-}
-
-pub fn and_then(fuzz_a: Fuzzer<a>, f: fn(a) -> Fuzzer<b>) -> Fuzzer<b> {
-  fn(s0) {
-    when fuzz_a(s0) is {
-      Some((s1, a)) -> f(a)(s1)
-      None -> None
-    }
-  }
-}
-
-pub fn map(fuzz_a: Fuzzer<a>, f: fn(a) -> b) -> Fuzzer<b> {
-  fn(s0) {
-    when fuzz_a(s0) is {
-      Some((s1, a)) -> Some((s1, f(a)))
-      None -> None
-    }
-  }
-}
-
-pub fn map2(fuzz_a: Fuzzer<a>, fuzz_b: Fuzzer<b>, f: fn(a, b) -> c) -> Fuzzer<c> {
-  fn(s0) {
-    when fuzz_a(s0) is {
-      Some((s1, a)) ->
-        when fuzz_b(s1) is {
-          Some((s2, b)) -> Some((s2, f(a, b)))
-          None -> None
-        }
-      None -> None
-    }
-  }
-}
-
-// Builders
-
-fn any_bool() -> Fuzzer<Bool> {
-  any_int |> map(fn(n) { n <= 127 })
-}
-
-fn any_list(fuzz_a: Fuzzer<a>) -> Fuzzer<List<a>> {
-  any_bool()
-    |> and_then(
-         fn(continue) {
-           if continue {
-             map2(fuzz_a, any_list(fuzz_a), fn(head, tail) { [head, ..tail] })
-           } else {
-             constant([])
-           }
-         },
-       )
-}
-
-fn any_season() -> Fuzzer<Season> {
-  any_int
-    |> and_then(
-         fn(i) {
-           let n = i % 3
-           if n == 0 {
-             any_bool() |> map(Winter)
-           } else if n == 1 {
-             constant(Spring(i))
-           } else if n == 2 {
-             constant(Summer)
-           } else {
-             constant(Fall)
-           }
-         },
-       )
-}
-
-fn length(xs: List<a>) -> Int {
-  when xs is {
-    [] -> 0
-    [_, ..tail] -> 1 + length(tail)
-  }
-}
-
-fn filter(xs: List<a>, f: fn(a) -> Bool) -> List<a> {
-  when xs is {
-    [] ->
-      []
-    [head, ..tail] ->
-      if f(head) {
-        [head, ..filter(tail, f)]
-      } else {
-        filter(tail, f)
-      }
-  }
-}
-
-// Properties
+use aiken/dict.{Dict}
+use aiken/fuzz.{Fuzzer}
+use aiken/int
 
 pub type Season {
-  Winter(Bool)
-  Spring(Int)
+  Winter
+  Spring
   Summer
   Fall
 }
 
-// test prop_is_never_summer(xs via any_list(any_season())) {
-//   filter(xs, fn(x) { x == Summer }) == []
-// }
+fn compare_season(a: Season, b: Season) -> Ordering {
+  let season_to_int =
+    fn(season) {
+      when season is {
+        Winter -> 0
+        Spring -> 1
+        Summer -> 2
+        Fall -> 3
+      }
+    }
 
-test prop_is_always_cold_in_winter(xs via any_list(any_season())) {
-  is_always_cold_in_winter(xs)
+  int.compare(season_to_int(a), season_to_int(b))
 }
 
-test prop_is_always_cold_in_winter_2() {
-  is_always_cold_in_winter([Winter(True)])
+fn any_year() -> Fuzzer<Dict<Season, Int>> {
+  fuzz.map4(
+    fuzz.any_int(),
+    fuzz.any_int(),
+    fuzz.any_int(),
+    fuzz.any_int(),
+    fn(a, b, c, d) {
+      dict.new()
+        |> dict.insert(Winter, a, compare_season)
+        |> dict.insert(Spring, b, compare_season)
+        |> dict.insert(Summer, c, compare_season)
+        |> dict.insert(Fall, d, compare_season)
+    },
+  )
 }
 
-fn is_always_cold_in_winter(xs: List<Season>) -> Bool {
-  when xs is {
-    [Winter(cold), ..tail] -> cold && is_always_cold_in_winter(tail)
-    _ -> True
+test prop_always_cold_in_winter(year via any_year()) {
+  when dict.get(year, Winter) is {
+    Some(temperature) -> temperature <= 10
+    _ -> fail @"failed to get?"
   }
 }