diff --git a/.gitignore b/.gitignore
index c60942fd7..3c202a89d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,6 +14,7 @@ __arkscript__/
 /*.ark
 *.ark.ir
 !tests/unittests/resources/BytecodeReaderSuite/*.arkc
+tools/*_hash.py
 
 # Generated files
 include/Ark/Constants.hpp
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 10c40f1e2..147f1ad5d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,9 +7,11 @@
 
 ### Added
 - added new macro `$gensym`, to generate a unique symbol identifier to use in macros
+- `append`, `concat`, and `pop` can be use as values
 
 ### Changed
 - all paths inside `if` should return a value, when used as an expression. If an `else` branch is missing, `nil` will be returned
+- new compile time error when trying to use `append!`, `concat!`, `pop!`, `@=` and `@@=` as values
 
 ### Removed
 
diff --git a/include/Ark/Builtins/Builtins.hpp b/include/Ark/Builtins/Builtins.hpp
index 2f7f0e151..275468711 100644
--- a/include/Ark/Builtins/Builtins.hpp
+++ b/include/Ark/Builtins/Builtins.hpp
@@ -163,6 +163,9 @@ namespace Ark::internal::Builtins
         ARK_BUILTIN(at);
         ARK_BUILTIN(atAt);
         ARK_BUILTIN(type);
+        ARK_BUILTIN(append_list);
+        ARK_BUILTIN(concat_list);
+        ARK_BUILTIN(pop_list);
     }
 }
 
diff --git a/src/arkreactor/Builtins/Builtins.cpp b/src/arkreactor/Builtins/Builtins.cpp
index 809fffa95..5e8dd6c0c 100644
--- a/src/arkreactor/Builtins/Builtins.cpp
+++ b/src/arkreactor/Builtins/Builtins.cpp
@@ -134,6 +134,9 @@ namespace Ark::internal::Builtins
         { "head", Value(Operators::head) },
         { "@", Value(Operators::at) },
         { "@@", Value(Operators::atAt) },
-        { "type", Value(Operators::type) }
+        { "type", Value(Operators::type) },
+        { "append", Value(Operators::append_list) },
+        { "concat", Value(Operators::concat_list) },
+        { "pop", Value(Operators::pop_list) }
     };
 }
diff --git a/src/arkreactor/Builtins/Operators.cpp b/src/arkreactor/Builtins/Operators.cpp
index e6ccee14b..77ef6cf9d 100644
--- a/src/arkreactor/Builtins/Operators.cpp
+++ b/src/arkreactor/Builtins/Operators.cpp
@@ -374,4 +374,70 @@ namespace Ark::internal::Builtins::Operators
 
         return Value(std::to_string(n[0].valueType()));
     }
+
+    // cppcheck-suppress constParameterReference
+    Value append_list(std::vector<Value>& n, VM* vm [[maybe_unused]])
+    {
+        if (n.size() < 2 || n[0].valueType() != ValueType::List)
+            throw types::TypeCheckingError(
+                "append",
+                { { types::Contract {
+                    { types::Typedef("list", ValueType::List),
+                      types::Typedef("value", ValueType::Any, /* is_variadic= */ true) } } } },
+                n);
+
+        for (Value& e : n | std::ranges::views::drop(1))
+            n[0].list().push_back(e);
+
+        return n[0];
+    }
+
+    // cppcheck-suppress constParameterReference
+    Value concat_list(std::vector<Value>& n, VM* vm [[maybe_unused]])
+    {
+        if (n.size() < 2 || n[0].valueType() != ValueType::List)
+            throw types::TypeCheckingError(
+                "concat",
+                { { types::Contract {
+                    { types::Typedef("list", ValueType::List),
+                      types::Typedef("value", ValueType::List, /* is_variadic= */ true) } } } },
+                n);
+
+        for (Value& e : n | std::ranges::views::drop(1))
+        {
+            if (e.valueType() != ValueType::List)
+                throw types::TypeCheckingError(
+                    "concat",
+                    { { types::Contract {
+                        { types::Typedef("dst", ValueType::List),
+                          types::Typedef("src", ValueType::List, /* is_variadic= */ true) } } } },
+                    n);
+
+            std::ranges::copy(e.list(), std::back_inserter(n[0].list()));
+        }
+
+        return n[0];
+    }
+
+    // cppcheck-suppress constParameterReference
+    Value pop_list(std::vector<Value>& n, VM* vm [[maybe_unused]])
+    {
+        if (!types::check(n, ValueType::List, ValueType::Number))
+            throw types::TypeCheckingError(
+                "pop",
+                { { types::Contract {
+                    { types::Typedef("list", ValueType::List),
+                      types::Typedef("index", ValueType::Number) } } } },
+                n);
+
+        long idx = static_cast<long>(n[1].number());
+        idx = idx < 0 ? static_cast<long>(n[0].list().size()) + idx : idx;
+        if (std::cmp_greater_equal(idx, n[0].list().size()) || idx < 0)
+            VM::throwVMError(
+                ErrorKind::Index,
+                fmt::format("pop index ({}) out of range (list size: {})", idx, n[0].list().size()));
+
+        n[0].list().erase(n[0].list().begin() + idx);
+        return n[0];
+    }
 }
diff --git a/src/arkreactor/Compiler/Lowerer/ASTLowerer.cpp b/src/arkreactor/Compiler/Lowerer/ASTLowerer.cpp
index 947dc8441..396d60fc5 100644
--- a/src/arkreactor/Compiler/Lowerer/ASTLowerer.cpp
+++ b/src/arkreactor/Compiler/Lowerer/ASTLowerer.cpp
@@ -320,6 +320,10 @@ namespace Ark::internal
 
         if (const auto it_builtin = getBuiltin(name))
             page(p).emplace_back(Instruction::BUILTIN, it_builtin.value());
+        else if (std::ranges::find(Language::UpdateRef, name) != Language::UpdateRef.end())
+            buildAndThrowError(fmt::format("`{}' updates a list in-place, and can not be used as a value. Prefer using their copy alternative (without the `!` at the end) when possible", name), x);
+        else if (name == Language::And || name == Language::Or)
+            buildAndThrowError(fmt::format("`{}' can not be used as a value like `+', where (let add +) (add 1 2) would be valid", name), x);
         else if (getOperator(name).has_value())
             buildAndThrowError(fmt::format("Found a freestanding operator: `{}`. It can not be used as value like `+', where (let add +) (add 1 2) would be valid", name), x);
         else
diff --git a/tests/unittests/resources/CompilerSuite/ir/operators.ark b/tests/unittests/resources/CompilerSuite/ir/operators.ark
index cb70addcf..4cf1cd6c6 100644
--- a/tests/unittests/resources/CompilerSuite/ir/operators.ark
+++ b/tests/unittests/resources/CompilerSuite/ir/operators.ark
@@ -23,4 +23,7 @@
   (head [])
   (@ [1 2] 1)
   (@@ [[1] [2] [3]] 0 0)
-  (type 12))
+  (type 12)
+  (append [] 1)
+  (concat [1] [2])
+  (pop [1] 0))
diff --git a/tests/unittests/resources/CompilerSuite/ir/operators.expected b/tests/unittests/resources/CompilerSuite/ir/operators.expected
index 4854cff50..0c3ee2703 100644
--- a/tests/unittests/resources/CompilerSuite/ir/operators.expected
+++ b/tests/unittests/resources/CompilerSuite/ir/operators.expected
@@ -66,7 +66,19 @@ page_0
 	AT_AT 0
 	LOAD_CONST 3
 	TYPE 0
-	CALL_BUILTIN 9, 22
+	LOAD_CONST 0
+	LIST 0
+	APPEND 1
+	LOAD_CONST 1
+	LIST 1
+	LOAD_CONST 0
+	LIST 1
+	CONCAT 1
+	LOAD_CONST 5
+	LOAD_CONST 0
+	LIST 1
+	POP_LIST 0
+	CALL_BUILTIN 9, 25
 .L0:
 	POP 0
 	HALT 0
diff --git a/tests/unittests/resources/CompilerSuite/ir/operators_as_builtins.ark b/tests/unittests/resources/CompilerSuite/ir/operators_as_builtins.ark
index 3e683477b..dee89e33a 100644
--- a/tests/unittests/resources/CompilerSuite/ir/operators_as_builtins.ark
+++ b/tests/unittests/resources/CompilerSuite/ir/operators_as_builtins.ark
@@ -1 +1 @@
-(print + - * / mod toNumber toString < <= > >= = != not len empty? nil? tail head @ @@ type)
+(print + - * / mod toNumber toString < <= > >= = != not len empty? nil? tail head @ @@ type append concat pop)
diff --git a/tests/unittests/resources/CompilerSuite/ir/operators_as_builtins.expected b/tests/unittests/resources/CompilerSuite/ir/operators_as_builtins.expected
index a53fb6aec..e0c95fe03 100644
--- a/tests/unittests/resources/CompilerSuite/ir/operators_as_builtins.expected
+++ b/tests/unittests/resources/CompilerSuite/ir/operators_as_builtins.expected
@@ -22,7 +22,10 @@ page_0
 	BUILTIN 88
 	BUILTIN 89
 	BUILTIN 90
-	CALL_BUILTIN 9, 22
+	BUILTIN 91
+	BUILTIN 92
+	BUILTIN 93
+	CALL_BUILTIN 9, 25
 .L0:
 	POP 0
 	HALT 0
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_and.ark b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_and.ark
new file mode 100644
index 000000000..e252e1a13
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_and.ark
@@ -0,0 +1,2 @@
+(let a and)
+(a 1 2)
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_and.expected b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_and.expected
new file mode 100644
index 000000000..cbe4782aa
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_and.expected
@@ -0,0 +1,6 @@
+In file tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_and.ark:1
+    1 | (let a and)
+      |        ^~~
+    2 | (a 1 2)
+    3 |
+        `and' can not be used as a value like `+', where (let add +) (add 1 2) would be valid
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_append_in_place.ark b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_append_in_place.ark
new file mode 100644
index 000000000..cc1b9450e
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_append_in_place.ark
@@ -0,0 +1,3 @@
+(let a append!)
+(mut b [])
+(a b 5)
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_append_in_place.expected b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_append_in_place.expected
new file mode 100644
index 000000000..bd0c586ff
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_append_in_place.expected
@@ -0,0 +1,6 @@
+In file tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_append_in_place.ark:1
+    1 | (let a append!)
+      |        ^~~~~~~
+    2 | (mut b [])
+    3 | (a b 5)
+        `append!' updates a list in-place, and can not be used as a value. Prefer using their copy alternative (without the `!` at the end) when possible
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_at_eq.ark b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_at_eq.ark
new file mode 100644
index 000000000..0910af27f
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_at_eq.ark
@@ -0,0 +1,3 @@
+(let a @@=)
+(mut b [[]])
+(a b 5 6 7)
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_at_eq.expected b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_at_eq.expected
new file mode 100644
index 000000000..c7ae8952c
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_at_eq.expected
@@ -0,0 +1,6 @@
+In file tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_at_eq.ark:1
+    1 | (let a @@=)
+      |        ^~~
+    2 | (mut b [[]])
+    3 | (a b 5 6 7)
+        `@@=' updates a list in-place, and can not be used as a value. Prefer using their copy alternative (without the `!` at the end) when possible
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_eq.ark b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_eq.ark
new file mode 100644
index 000000000..5b4b142bb
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_eq.ark
@@ -0,0 +1,3 @@
+(let a @=)
+(mut b [])
+(a b 5 6)
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_eq.expected b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_eq.expected
new file mode 100644
index 000000000..7ef5cc360
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_eq.expected
@@ -0,0 +1,6 @@
+In file tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_at_eq.ark:1
+    1 | (let a @=)
+      |        ^~
+    2 | (mut b [])
+    3 | (a b 5 6)
+        `@=' updates a list in-place, and can not be used as a value. Prefer using their copy alternative (without the `!` at the end) when possible
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_concat_in_place.ark b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_concat_in_place.ark
new file mode 100644
index 000000000..f408fe167
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_concat_in_place.ark
@@ -0,0 +1,3 @@
+(let a concat!)
+(mut b [])
+(a b [5])
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_concat_in_place.expected b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_concat_in_place.expected
new file mode 100644
index 000000000..eaf16f843
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_concat_in_place.expected
@@ -0,0 +1,6 @@
+In file tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_concat_in_place.ark:1
+    1 | (let a concat!)
+      |        ^~~~~~~
+    2 | (mut b [])
+    3 | (a b [5])
+        `concat!' updates a list in-place, and can not be used as a value. Prefer using their copy alternative (without the `!` at the end) when possible
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_or.ark b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_or.ark
new file mode 100644
index 000000000..8f0235833
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_or.ark
@@ -0,0 +1,2 @@
+(let a or)
+(a 1 2)
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_or.expected b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_or.expected
new file mode 100644
index 000000000..99d007541
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_or.expected
@@ -0,0 +1,6 @@
+In file tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_or.ark:1
+    1 | (let a or)
+      |        ^~
+    2 | (a 1 2)
+    3 |
+        `or' can not be used as a value like `+', where (let add +) (add 1 2) would be valid
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_pop_in_place.ark b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_pop_in_place.ark
new file mode 100644
index 000000000..d23660fe1
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_pop_in_place.ark
@@ -0,0 +1,3 @@
+(let a pop!)
+(mut b [])
+(a b 5)
diff --git a/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_pop_in_place.expected b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_pop_in_place.expected
new file mode 100644
index 000000000..48d103142
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_pop_in_place.expected
@@ -0,0 +1,6 @@
+In file tests/unittests/resources/DiagnosticsSuite/compileTime/let_a_pop_in_place.ark:1
+    1 | (let a pop!)
+      |        ^~~~
+    2 | (mut b [])
+    3 | (a b 5)
+        `pop!' updates a list in-place, and can not be used as a value. Prefer using their copy alternative (without the `!` at the end) when possible
diff --git a/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range.ark b/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range.ark
new file mode 100644
index 000000000..ce39dba95
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range.ark
@@ -0,0 +1 @@
+(apply pop [[1 2 3] 4])
diff --git a/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range.expected b/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range.expected
new file mode 100644
index 000000000..93d0b121e
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range.expected
@@ -0,0 +1,6 @@
+IndexError: pop index (4) out of range (list size: 3)
+
+In file tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range.ark:1
+    1 | (apply pop [[1 2 3] 4])
+      | ^~~~~~~~~~~~~~~~~~~~~~
+    2 |
diff --git a/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range_neg.ark b/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range_neg.ark
new file mode 100644
index 000000000..043dcaee0
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range_neg.ark
@@ -0,0 +1 @@
+(apply pop [[1 2 3] -4])
diff --git a/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range_neg.expected b/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range_neg.expected
new file mode 100644
index 000000000..5823bfbc3
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range_neg.expected
@@ -0,0 +1,6 @@
+IndexError: pop index (-1) out of range (list size: 3)
+
+In file tests/unittests/resources/DiagnosticsSuite/runtime/apply_pop_out_of_range_neg.ark:1
+    1 | (apply pop [[1 2 3] -4])
+      | ^~~~~~~~~~~~~~~~~~~~~~~
+    2 |
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_list.ark b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_list.ark
new file mode 100644
index 000000000..f314ce7a9
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_list.ark
@@ -0,0 +1 @@
+(apply append [[1]])
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_list.expected b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_list.expected
new file mode 100644
index 000000000..2ea97ec6b
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_list.expected
@@ -0,0 +1,13 @@
+Function append expected at least 2 arguments but got 1
+Call
+  ↳ (append [1])
+Signature
+  ↳ (append list value)
+Arguments
+  → `list' (expected List) ✓
+  → variadic `value' (expected any) was not provided
+
+In file tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_list.ark:1
+    1 | (apply append [[1]])
+      | ^~~~~~~~~~~~~~~~~~~
+    2 |
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_num_num.ark b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_num_num.ark
new file mode 100644
index 000000000..08c235b21
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_num_num.ark
@@ -0,0 +1 @@
+(apply append [1 2])
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_num_num.expected b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_num_num.expected
new file mode 100644
index 000000000..93ee3e325
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_num_num.expected
@@ -0,0 +1,13 @@
+Function append expected at least 2 arguments and got 2
+Call
+  ↳ (append 1 2)
+Signature
+  ↳ (append list value)
+Arguments
+  → `list' (expected List), got 1 (Number)
+  → variadic `value' (expected any)
+
+In file tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_append_num_num.ark:1
+    1 | (apply append [1 2])
+      | ^~~~~~~~~~~~~~~~~~~
+    2 |
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list.ark b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list.ark
new file mode 100644
index 000000000..1084344ce
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list.ark
@@ -0,0 +1 @@
+(apply concat [[1]])
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list.expected b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list.expected
new file mode 100644
index 000000000..ceff106aa
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list.expected
@@ -0,0 +1,13 @@
+Function concat expected at least 2 arguments but got 1
+Call
+  ↳ (concat [1])
+Signature
+  ↳ (concat list value)
+Arguments
+  → `list' (expected List) ✓
+  → variadic `value' (expected List) was not provided
+
+In file tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list.ark:1
+    1 | (apply concat [[1]])
+      | ^~~~~~~~~~~~~~~~~~~
+    2 |
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list_num.ark b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list_num.ark
new file mode 100644
index 000000000..cb24dedc7
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list_num.ark
@@ -0,0 +1 @@
+(apply concat [[1] 1])
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list_num.expected b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list_num.expected
new file mode 100644
index 000000000..29fe2fddb
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list_num.expected
@@ -0,0 +1,14 @@
+Function concat expected at least 2 arguments and got 2
+Call
+  ↳ (concat [1] 1)
+Signature
+  ↳ (concat dst src)
+Arguments
+  → `dst' (expected List) ✓
+  → variadic `src' (expected List): 1 argument do not match:
+    1 (Number) ×
+
+In file tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_list_num.ark:1
+    1 | (apply concat [[1] 1])
+      | ^~~~~~~~~~~~~~~~~~~~~
+    2 |
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_num.ark b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_num.ark
new file mode 100644
index 000000000..0b2223261
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_num.ark
@@ -0,0 +1 @@
+(apply concat [1])
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_num.expected b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_num.expected
new file mode 100644
index 000000000..246fcabb0
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_num.expected
@@ -0,0 +1,13 @@
+Function concat expected at least 2 arguments but got 1
+Call
+  ↳ (concat 1)
+Signature
+  ↳ (concat list value)
+Arguments
+  → `list' (expected List), got 1 (Number)
+  → variadic `value' (expected List) was not provided
+
+In file tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_concat_num.ark:1
+    1 | (apply concat [1])
+      | ^~~~~~~~~~~~~~~~~
+    2 |
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_pop_num_num.ark b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_pop_num_num.ark
new file mode 100644
index 000000000..b52914ae2
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_pop_num_num.ark
@@ -0,0 +1 @@
+(apply pop [1 1])
diff --git a/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_pop_num_num.expected b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_pop_num_num.expected
new file mode 100644
index 000000000..b783dc7ae
--- /dev/null
+++ b/tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_pop_num_num.expected
@@ -0,0 +1,13 @@
+Function pop expected 2 arguments
+Call
+  ↳ (pop 1 1)
+Signature
+  ↳ (pop list index)
+Arguments
+  → `list' (expected List), got 1 (Number)
+  → `index' (expected Number) ✓
+
+In file tests/unittests/resources/DiagnosticsSuite/typeChecking/apply_pop_num_num.ark:1
+    1 | (apply pop [1 1])
+      | ^~~~~~~~~~~~~~~~
+    2 |
diff --git a/tests/unittests/resources/LangSuite/operators-tests.ark b/tests/unittests/resources/LangSuite/operators-tests.ark
index ee4d29eb3..5e89ef5b2 100644
--- a/tests/unittests/resources/LangSuite/operators-tests.ark
+++ b/tests/unittests/resources/LangSuite/operators-tests.ark
@@ -190,4 +190,18 @@
     (test:eq (apply type [1]) (type 1))
     (test:eq (apply type [1]) "Number")
     (test:eq (apply type [nil]) (type nil))
-    (test:eq (apply type [nil]) "Nil") })})
+    (test:eq (apply type [nil]) "Nil") })
+
+  (test:case "append" {
+    (test:eq (apply append [[] 1]) [1])
+    (test:eq (apply append [[] 1 2]) [1 2])
+    (test:eq (apply append [[] 1 2 3]) [1 2 3]) })
+
+  (test:case "concat" {
+    (test:eq (apply concat [[] [1]]) [1])
+    (test:eq (apply concat [[] [1] [2 3]]) [1 2 3])
+    (test:eq (apply concat [[] [1] [2 3] [] [4 5 6]]) [1 2 3 4 5 6]) })
+
+  (test:case "pop" {
+    (test:eq (apply pop [[1 2] 0]) [2])
+    (test:eq (apply pop [[1] 0]) []) }) })
diff --git a/tests/unittests/resources/LangSuite/weird-tests.ark b/tests/unittests/resources/LangSuite/weird-tests.ark
index da0811b06..e798b61f6 100644
--- a/tests/unittests/resources/LangSuite/weird-tests.ark
+++ b/tests/unittests/resources/LangSuite/weird-tests.ark
@@ -15,7 +15,7 @@
 
   (test:case "list:map with let" {
     (mut output [])
-    (list:map (let a [0 1]) f1)
+    (list:map (let z [0 1]) f1)
     (test:eq output [0 1]) })
 
   (test:case "(Q ((let Q f1) 0))" {
@@ -63,4 +63,17 @@
       (or false (if 0 0))
       b }))
 
-    (test:eq (g 1 2) 2) }) })
+    (test:eq (g 1 2) 2) })
+
+  (test:case "append, concat, pop as values" {
+    (let data [1 2 3])
+    (let a append)
+    (let c concat)
+    (let p pop)
+
+    (test:eq (type a) "CProc")
+    (test:eq (type c) "CProc")
+    (test:eq (type p) "CProc")
+    (test:eq (a data 4) [1 2 3 4])
+    (test:eq (c data [4 5]) [1 2 3 4 5])
+    (test:eq (p data 1) [1 3]) }) })