diff --git a/src/compiler/Compile.go b/src/compiler/Compile.go
index f62943c..ae3c437 100644
--- a/src/compiler/Compile.go
+++ b/src/compiler/Compile.go
@@ -11,6 +11,7 @@ import (
 func Compile(constants <-chan *core.Constant, files <-chan *fs.File, functions <-chan *core.Function, structs <-chan *types.Struct, errs <-chan error) (Result, error) {
 	all := core.Environment{
 		Files:     make([]*fs.File, 0, 8),
+		Extern:    make(map[string]struct{}, 0),
 		Functions: make(map[string]*core.Function, 32),
 		Structs:   make(map[string]*types.Struct, 8),
 		Constants: make(map[string]*core.Constant, 8),
@@ -29,6 +30,10 @@ func Compile(constants <-chan *core.Constant, files <-chan *fs.File, functions <
 			function.All = &all
 			all.Functions[function.UniqueName] = function
 
+			if function.IsExtern() {
+				all.Extern[function.Package] = struct{}{}
+			}
+
 		case structure, ok := <-structs:
 			if !ok {
 				structs = nil
diff --git a/src/core/CompileCall.go b/src/core/CompileCall.go
index fec090a..7e47f48 100644
--- a/src/core/CompileCall.go
+++ b/src/core/CompileCall.go
@@ -3,7 +3,9 @@ package core
 import (
 	"git.urbach.dev/cli/q/src/asm"
 	"git.urbach.dev/cli/q/src/errors"
+	"git.urbach.dev/cli/q/src/eval"
 	"git.urbach.dev/cli/q/src/expression"
+	"git.urbach.dev/cli/q/src/token"
 	"git.urbach.dev/cli/q/src/types"
 )
 
@@ -12,17 +14,8 @@ import (
 // Registers that are in use must be saved if they are modified by the function.
 // After the function call, they must be restored in reverse order.
 func (f *Function) CompileCall(root *expression.Expression) ([]types.Type, error) {
-	var (
-		pkg      = f.Package
-		pkgNode  *expression.Expression
-		name     string
-		nameNode = root.Children[0]
-		fn       *Function
-		exists   bool
-	)
-
-	if nameNode.IsLeaf() {
-		name = nameNode.Token.Text(f.File.Bytes)
+	if root.Children[0].Token.Kind == token.Identifier {
+		name := root.Children[0].Token.Text(f.File.Bytes)
 
 		switch name {
 		case "len":
@@ -37,63 +30,56 @@ func (f *Function) CompileCall(root *expression.Expression) ([]types.Type, error
 		case "store":
 			return nil, f.CompileMemoryStore(root)
 		}
-	} else {
-		pkgNode = nameNode.Children[0]
-		nameNode = nameNode.Children[1]
-
-		pkg = pkgNode.Token.Text(f.File.Bytes)
-		name = nameNode.Token.Text(f.File.Bytes)
 	}
 
-	if f.UniqueName == "core.init" && pkg == "main" && name == "main" {
-		f.Label(asm.CALL, "main.main")
-		return nil, nil
-	}
-
-	fn, exists = f.All.Functions[pkg+"."+name]
-
-	if !exists {
-		variable := f.VariableByName(name)
-
-		if variable != nil {
-			f.Register(asm.CALL, variable.Value.Register)
-			return nil, nil
-		}
-
-		return nil, errors.New(&errors.UnknownFunction{Name: name}, f.File, nameNode.Token.Position)
-	}
-
-	if pkg != f.File.Package && !fn.IsExtern() {
-		if f.File.Imports == nil {
-			return nil, errors.New(&errors.UnknownPackage{Name: pkg}, f.File, pkgNode.Token.Position)
-		}
-
-		imp, exists := f.File.Imports[pkg]
-
-		if !exists {
-			return nil, errors.New(&errors.UnknownPackage{Name: pkg}, f.File, pkgNode.Token.Position)
-		}
-
-		imp.Used = true
-	}
-
-	parameters := root.Children[1:]
-
-	if len(parameters) != len(fn.Input) {
-		return nil, errors.New(&errors.ParameterCountMismatch{Function: fn.Name, Count: len(parameters), ExpectedCount: len(fn.Input)}, f.File, nameNode.Token.End())
-	}
-
-	if fn.IsExtern() {
-		return f.CallExtern(fn, parameters)
-	}
-
-	registers := f.CPU.Input[:len(parameters)]
-	err := f.ExpressionsToRegisters(parameters, registers, fn.Input, true)
+	value, err := f.Evaluate(root.Children[0])
 
 	if err != nil {
 		return nil, err
 	}
 
-	f.CallSafe(fn, registers)
-	return fn.OutputTypes, nil
+	parameters := root.Children[1:]
+	registers := f.CPU.Input[:len(parameters)]
+
+	switch value := value.(type) {
+	case *eval.Label:
+		fn, exists := f.All.Functions[value.Label]
+
+		if !exists {
+			if value.Label == "main.main" && f.UniqueName == "core.init" {
+				f.Label(asm.CALL, "main.main")
+				return nil, nil
+			}
+
+			return nil, errors.New(&errors.UnknownIdentifier{Name: value.Label}, f.File, root.Children[0].Token.Position)
+		}
+
+		if len(parameters) != len(fn.Input) {
+			return nil, errors.New(&errors.ParameterCountMismatch{Function: fn.Name, Count: len(parameters), ExpectedCount: len(fn.Input)}, f.File, root.Children[0].Token.End())
+		}
+
+		if fn.IsExtern() {
+			return f.CallExtern(fn, parameters)
+		}
+
+		err := f.ExpressionsToRegisters(parameters, registers, fn.Input, true)
+
+		if err != nil {
+			return nil, err
+		}
+
+		f.CallSafe(fn, registers)
+		return fn.OutputTypes, nil
+
+	case *eval.Register:
+		f.Register(asm.CALL, value.Register)
+
+	case *eval.Memory:
+		tmp := f.NewRegister()
+		f.MemoryRegister(asm.LOAD, value.Memory, tmp)
+		f.Register(asm.CALL, tmp)
+		f.FreeRegister(tmp)
+	}
+
+	return nil, nil
 }
diff --git a/src/core/Environment.go b/src/core/Environment.go
index e2a1354..c27828a 100644
--- a/src/core/Environment.go
+++ b/src/core/Environment.go
@@ -8,6 +8,7 @@ import (
 // Environment holds information about the entire build.
 type Environment struct {
 	Constants map[string]*Constant
+	Extern    map[string]struct{}
 	Functions map[string]*Function
 	Structs   map[string]*types.Struct
 	Files     []*fs.File
diff --git a/src/core/EvaluateDot.go b/src/core/EvaluateDot.go
index 944ea02..69f078c 100644
--- a/src/core/EvaluateDot.go
+++ b/src/core/EvaluateDot.go
@@ -59,19 +59,24 @@ func (f *Function) EvaluateDot(expr *expression.Expression) (eval.Value, error)
 		return value, nil
 	}
 
-	uniqueName := fmt.Sprintf("%s.%s", leftText, rightText)
-	function, exists := f.All.Functions[uniqueName]
+	if leftText != "main" {
+		imp, exists := f.File.Imports[leftText]
 
-	if exists {
-		f.File.Imports[leftText].Used = true
+		if exists {
+			imp.Used = true
+		} else {
+			_, exists := f.All.Extern[leftText]
 
-		value := &eval.Label{
-			Typ:   types.AnyPointer,
-			Label: function.UniqueName,
+			if !exists {
+				return nil, errors.New(&errors.UnknownPackage{Name: leftText}, f.File, left.Token.Position)
+			}
 		}
-
-		return value, nil
 	}
 
-	return nil, errors.New(&errors.UnknownIdentifier{Name: uniqueName}, f.File, left.Token.Position)
+	value := &eval.Label{
+		Typ:   types.AnyPointer,
+		Label: fmt.Sprintf("%s.%s", leftText, rightText),
+	}
+
+	return value, nil
 }
diff --git a/src/errors/UnknownFunction.go b/src/errors/UnknownFunction.go
deleted file mode 100644
index a2b7e4e..0000000
--- a/src/errors/UnknownFunction.go
+++ /dev/null
@@ -1,18 +0,0 @@
-package errors
-
-import "fmt"
-
-// UnknownFunction represents unknown function errors.
-type UnknownFunction struct {
-	Name        string
-	CorrectName string
-}
-
-// Error generates the string representation.
-func (err *UnknownFunction) Error() string {
-	if err.CorrectName != "" {
-		return fmt.Sprintf("Unknown function '%s', did you mean '%s'?", err.Name, err.CorrectName)
-	}
-
-	return fmt.Sprintf("Unknown function '%s'", err.Name)
-}
diff --git a/tests/errors/MissingBlockStart2.q b/tests/errors/MissingBlockStart2.q
new file mode 100644
index 0000000..7e12b77
--- /dev/null
+++ b/tests/errors/MissingBlockStart2.q
@@ -0,0 +1,3 @@
+main() {
+	loop
+}
\ No newline at end of file
diff --git a/tests/errors/UnknownFunction2.q b/tests/errors/UnknownFunction2.q
deleted file mode 100644
index c31b354..0000000
--- a/tests/errors/UnknownFunction2.q
+++ /dev/null
@@ -1,3 +0,0 @@
-main() {
-	x := 1 + f(x)
-}
\ No newline at end of file
diff --git a/tests/errors/UnknownFunction.q b/tests/errors/UnknownIdentifier4.q
similarity index 100%
rename from tests/errors/UnknownFunction.q
rename to tests/errors/UnknownIdentifier4.q
diff --git a/tests/errors/UnknownIdentifier5.q b/tests/errors/UnknownIdentifier5.q
new file mode 100644
index 0000000..5d38d8e
--- /dev/null
+++ b/tests/errors/UnknownIdentifier5.q
@@ -0,0 +1,3 @@
+main() {
+	x := 1 + unknown(x)
+}
\ No newline at end of file
diff --git a/tests/errors_test.go b/tests/errors_test.go
index 95a5424..9403bfc 100644
--- a/tests/errors_test.go
+++ b/tests/errors_test.go
@@ -39,6 +39,7 @@ var errs = []struct {
 	{"MissingBlockEnd.q", errors.MissingBlockEnd},
 	{"MissingBlockEnd2.q", errors.MissingBlockEnd},
 	{"MissingBlockStart.q", errors.MissingBlockStart},
+	{"MissingBlockStart2.q", errors.MissingBlockStart},
 	{"MissingExpression.q", errors.MissingExpression},
 	{"MissingGroupEnd.q", errors.MissingGroupEnd},
 	{"MissingGroupStart.q", errors.MissingGroupStart},
@@ -52,11 +53,11 @@ var errs = []struct {
 	{"ReturnCountMismatch.q", &errors.ReturnCountMismatch{Count: 1, ExpectedCount: 0}},
 	{"TypeMismatch.q", &errors.TypeMismatch{Expected: "*any", Encountered: "int", ParameterName: "p"}},
 	{"TypeMismatch2.q", &errors.TypeMismatch{Expected: "[]any", Encountered: "int", ParameterName: "array"}},
-	{"UnknownFunction.q", &errors.UnknownFunction{Name: "unknown"}},
-	{"UnknownFunction2.q", &errors.UnknownFunction{Name: "f"}},
 	{"UnknownIdentifier.q", &errors.UnknownIdentifier{Name: "x"}},
 	{"UnknownIdentifier2.q", &errors.UnknownIdentifier{Name: "x"}},
 	{"UnknownIdentifier3.q", &errors.UnknownIdentifier{Name: "x"}},
+	{"UnknownIdentifier4.q", &errors.UnknownIdentifier{Name: "unknown"}},
+	{"UnknownIdentifier5.q", &errors.UnknownIdentifier{Name: "unknown"}},
 	{"UnknownPackage.q", &errors.UnknownPackage{Name: "sys"}},
 	{"UnknownType.q", &errors.UnknownType{Name: "unknown"}},
 	{"UnknownType2.q", &errors.UnknownType{Name: "unknown"}},
diff --git a/tests/programs/function-pointer-field.q b/tests/programs/function-pointer-field.q
new file mode 100644
index 0000000..89894b9
--- /dev/null
+++ b/tests/programs/function-pointer-field.q
@@ -0,0 +1,11 @@
+import core
+
+struct Struct {
+	func *any
+}
+
+main() {
+	s := new(Struct)
+	s.func = core.exit
+	s.func()
+}
\ No newline at end of file
diff --git a/tests/programs/loop-in-loop.q b/tests/programs/loop-in-loop.q
new file mode 100644
index 0000000..969ace6
--- /dev/null
+++ b/tests/programs/loop-in-loop.q
@@ -0,0 +1,21 @@
+import sys
+
+main() {
+	x := 0
+
+	loop {
+		for 0..10 {
+			x += 1
+		}
+
+		assert x == 10
+
+		loop {
+			x -= 1
+
+			if x == 0 {
+				sys.exit(0)
+			}
+		}
+	}
+}
\ No newline at end of file
diff --git a/tests/programs/loop-infinite.q b/tests/programs/loop.q
similarity index 100%
rename from tests/programs/loop-infinite.q
rename to tests/programs/loop.q
diff --git a/tests/programs_test.go b/tests/programs_test.go
index 369c4af..a1e76ce 100644
--- a/tests/programs_test.go
+++ b/tests/programs_test.go
@@ -58,8 +58,9 @@ var programs = []struct {
 	{"branch-save", 0},
 	{"jump-near", 0},
 	{"switch", 0},
-	{"loop-infinite", 0},
+	{"loop", 0},
 	{"loop-lifetime", 0},
+	{"loop-in-loop", 0},
 	{"for", 0},
 	{"memory-free", 0},
 	{"out-of-memory", 0},
@@ -69,6 +70,7 @@ var programs = []struct {
 	{"len", 0},
 	{"cast", 0},
 	{"function-pointer", 0},
+	{"function-pointer-field", 0},
 }
 
 func TestPrograms(t *testing.T) {