diff --git a/.gitignore b/.gitignore
index a6ce85f..a9a9f7c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -78,8 +78,13 @@ fabric.properties
 .idea/caches/build_file_checksums.ser
 
 *~
+*-e
+*.so
 *.bak
 *.txt
+*.swo
+*.swn
+.DS_Store
 
 /dist
 /monkey-lang
\ No newline at end of file
diff --git a/builtins/args.go b/builtins/args.go
new file mode 100644
index 0000000..9c92379
--- /dev/null
+++ b/builtins/args.go
@@ -0,0 +1,12 @@
+package builtins
+
+import "monkey/object"
+
+// Args  ...
+func Args(args ...object.Object) object.Object {
+	elements := make([]object.Object, len(object.Arguments))
+	for i, arg := range object.Arguments {
+		elements[i] = &object.String{Value: arg}
+	}
+	return &object.Array{Elements: elements}
+}
diff --git a/object/builtin_assert.go b/builtins/assert.go
similarity index 55%
rename from object/builtin_assert.go
rename to builtins/assert.go
index 0b88af7..5f52e54 100644
--- a/object/builtin_assert.go
+++ b/builtins/assert.go
@@ -1,4 +1,6 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import (
 	"fmt"
@@ -6,22 +8,22 @@ import (
 )
 
 // Assert ...
-func Assert(args ...Object) Object {
+func Assert(args ...object.Object) object.Object {
 	if len(args) != 2 {
 		return newError("wrong number of arguments. got=%d, want=2",
 			len(args))
 	}
-	if args[0].Type() != BOOLEAN_OBJ {
+	if args[0].Type() != object.BOOLEAN_OBJ {
 		return newError("argument #1 to `assert` must be BOOLEAN, got %s",
 			args[0].Type())
 	}
-	if args[1].Type() != STRING_OBJ {
+	if args[1].Type() != object.STRING_OBJ {
 		return newError("argument #2 to `assert` must be STRING, got %s",
 			args[0].Type())
 	}
 
-	if !args[0].(*Boolean).Value {
-		fmt.Printf("Assertion Error: %s", args[1].(*String).Value)
+	if !args[0].(*object.Boolean).Value {
+		fmt.Printf("Assertion Error: %s", args[1].(*object.String).Value)
 		os.Exit(1)
 	}
 
diff --git a/builtins/bool.go b/builtins/bool.go
new file mode 100644
index 0000000..8dc6cdb
--- /dev/null
+++ b/builtins/bool.go
@@ -0,0 +1,40 @@
+package builtins
+
+import "monkey/object"
+
+// Bool ...
+func Bool(args ...object.Object) object.Object {
+	if len(args) != 1 {
+		return newError("wrong number of arguments. got=%d, want=1", len(args))
+	}
+
+	switch arg := args[0].(type) {
+	case *object.Null:
+		return &object.Boolean{Value: false}
+	case *object.Boolean:
+		return arg
+	case *object.Integer:
+		if arg.Value == 0 {
+			return &object.Boolean{Value: false}
+		}
+		return &object.Boolean{Value: true}
+	case *object.String:
+		if len(arg.Value) > 0 {
+			return &object.Boolean{Value: true}
+		}
+		return &object.Boolean{Value: false}
+	case *object.Array:
+		if len(arg.Elements) > 0 {
+			return &object.Boolean{Value: true}
+		}
+		return &object.Boolean{Value: false}
+	case *object.Hash:
+		if len(arg.Pairs) > 0 {
+			return &object.Boolean{Value: true}
+		}
+		return &object.Boolean{Value: false}
+
+	default:
+		return newError("argument to `bool` not supported, got=%s", args[0].Type())
+	}
+}
diff --git a/object/builtins.go b/builtins/builtins.go
similarity index 77%
rename from object/builtins.go
rename to builtins/builtins.go
index f063a66..5ecfeda 100644
--- a/object/builtins.go
+++ b/builtins/builtins.go
@@ -1,12 +1,13 @@
-package object
+package builtins
 
 import (
 	"fmt"
+	"monkey/object"
 	"sort"
 )
 
 // Builtins ...
-var Builtins = map[string]*Builtin{
+var Builtins = map[string]*object.Builtin{
 	"len":    {Name: "len", Fn: Len},
 	"input":  {Name: "input", Fn: Input},
 	"print":  {Name: "print", Fn: Print},
@@ -20,7 +21,7 @@ var Builtins = map[string]*Builtin{
 	"bool":   {Name: "bool", Fn: Bool},
 	"int":    {Name: "int", Fn: Int},
 	"str":    {Name: "str", Fn: Str},
-	"typeof": {Name: "typeof", Fn: TypeOf},
+	"type":   {Name: "type", Fn: TypeOf},
 	"args":   {Name: "args", Fn: Args},
 	"lower":  {Name: "lower", Fn: Lower},
 	"upper":  {Name: "upper", Fn: Upper},
@@ -29,10 +30,11 @@ var Builtins = map[string]*Builtin{
 	"find":   {Name: "find", Fn: Find},
 	"read":   {Name: "read", Fn: Read},
 	"write":  {Name: "write", Fn: Write},
+	"ffi":    {Name: "ffi", Fn: FFI},
 }
 
 // BuiltinsIndex ...
-var BuiltinsIndex []*Builtin
+var BuiltinsIndex []*object.Builtin
 
 func init() {
 	var keys []string
@@ -46,6 +48,6 @@ func init() {
 	}
 }
 
-func newError(format string, a ...interface{}) *Error {
-	return &Error{Message: fmt.Sprintf(format, a...)}
+func newError(format string, a ...interface{}) *object.Error {
+	return &object.Error{Message: fmt.Sprintf(format, a...)}
 }
diff --git a/builtins/exit.go b/builtins/exit.go
new file mode 100644
index 0000000..0bcf42c
--- /dev/null
+++ b/builtins/exit.go
@@ -0,0 +1,19 @@
+package builtins
+
+import "monkey/object"
+
+// Exit ...
+func Exit(args ...object.Object) object.Object {
+	var status int
+	if len(args) == 1 {
+		if args[0].Type() != object.INTEGER_OBJ {
+			return newError("argument to `exit` must be INTEGER, got %s",
+				args[0].Type())
+		}
+		status = int(args[0].(*object.Integer).Value)
+	}
+
+	object.ExitFunction(status)
+
+	return nil
+}
diff --git a/builtins/ffi.go b/builtins/ffi.go
new file mode 100644
index 0000000..c237abd
--- /dev/null
+++ b/builtins/ffi.go
@@ -0,0 +1,40 @@
+package builtins
+
+import "monkey/object"
+
+import (
+	"fmt"
+	"plugin"
+)
+
+// FFI ...
+func FFI(args ...object.Object) object.Object {
+	if len(args) != 2 {
+		return newError("wrong number of arguments. got=%d, want=2",
+			len(args))
+	}
+
+	arg, ok := args[0].(*object.String)
+	if !ok {
+		return newError("argument #1 to `ffi` expected to be `str` got=%T", args[0].Type())
+	}
+	name := arg.Value
+
+	arg, ok = args[1].(*object.String)
+	if !ok {
+		return newError("argument #2 to `ffi` expected to be `str` got=%T", args[0].Type())
+	}
+	symbol := arg.Value
+
+	p, err := plugin.Open(fmt.Sprintf("%s.so", name))
+	if err != nil {
+		return newError("error loading plugin: %s", err)
+	}
+
+	v, err := p.Lookup(symbol)
+	if err != nil {
+		return newError("error finding symbol: %s", err)
+	}
+
+	return &object.Builtin{Name: symbol, Fn: v.(func(...object.Object) object.Object)}
+}
diff --git a/object/builtin_find.go b/builtins/find.go
similarity index 54%
rename from object/builtin_find.go
rename to builtins/find.go
index 422b466..7664989 100644
--- a/object/builtin_find.go
+++ b/builtins/find.go
@@ -1,33 +1,35 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import (
 	"strings"
 )
 
 // Find ...
-func Find(args ...Object) Object {
+func Find(args ...object.Object) object.Object {
 	if len(args) != 2 {
 		return newError("wrong number of arguments. got=%d, want=2",
 			len(args))
 	}
 
-	if haystack, ok := args[0].(*String); ok {
-		if needle, ok := args[1].(*String); ok {
+	if haystack, ok := args[0].(*object.String); ok {
+		if needle, ok := args[1].(*object.String); ok {
 			index := strings.Index(haystack.Value, needle.Value)
-			return &Integer{Value: int64(index)}
+			return &object.Integer{Value: int64(index)}
 		} else {
 			return newError("expected arg #2 to be `str` got got=%T", args[1])
 		}
-	} else if haystack, ok := args[0].(*Array); ok {
+	} else if haystack, ok := args[0].(*object.Array); ok {
 		needle := args[1]
 		index := -1
 		for i, el := range haystack.Elements {
-			if cmp, ok := el.(Comparable); ok && cmp.Equal(needle) {
+			if cmp, ok := el.(object.Comparable); ok && cmp.Equal(needle) {
 				index = i
 				break
 			}
 		}
-		return &Integer{Value: int64(index)}
+		return &object.Integer{Value: int64(index)}
 	} else {
 		return newError("expected arg #1 to be `str` or `array` got got=%T", args[0])
 	}
diff --git a/object/builtin_first.go b/builtins/first.go
similarity index 62%
rename from object/builtin_first.go
rename to builtins/first.go
index 959f250..b25bac3 100644
--- a/object/builtin_first.go
+++ b/builtins/first.go
@@ -1,17 +1,19 @@
-package object
+package builtins
+
+import "monkey/object"
 
 // First ...
-func First(args ...Object) Object {
+func First(args ...object.Object) object.Object {
 	if len(args) != 1 {
 		return newError("wrong number of arguments. got=%d, want=1",
 			len(args))
 	}
-	if args[0].Type() != ARRAY_OBJ {
+	if args[0].Type() != object.ARRAY_OBJ {
 		return newError("argument to `first` must be array, got %s",
 			args[0].Type())
 	}
 
-	arr := args[0].(*Array)
+	arr := args[0].(*object.Array)
 	if len(arr.Elements) > 0 {
 		return arr.Elements[0]
 	}
diff --git a/object/builtin_input.go b/builtins/input.go
similarity index 70%
rename from object/builtin_input.go
rename to builtins/input.go
index 4be0858..f75a449 100644
--- a/object/builtin_input.go
+++ b/builtins/input.go
@@ -1,4 +1,6 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import (
 	"bufio"
@@ -8,9 +10,9 @@ import (
 )
 
 // Input ...
-func Input(args ...Object) Object {
+func Input(args ...object.Object) object.Object {
 	if len(args) > 0 {
-		obj, ok := args[0].(*String)
+		obj, ok := args[0].(*object.String)
 		if !ok {
 			return newError(
 				"argument to `input` not supported, got %s",
@@ -26,5 +28,5 @@ func Input(args ...Object) Object {
 	if err != nil && err != io.EOF {
 		return newError(fmt.Sprintf("error reading input from stdin: %s", err))
 	}
-	return &String{Value: string(line)}
+	return &object.String{Value: string(line)}
 }
diff --git a/object/builtin_int.go b/builtins/int.go
similarity index 61%
rename from object/builtin_int.go
rename to builtins/int.go
index 6654fe7..d0cc2a5 100644
--- a/object/builtin_int.go
+++ b/builtins/int.go
@@ -1,28 +1,30 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import "strconv"
 
 // Int ...
-func Int(args ...Object) Object {
+func Int(args ...object.Object) object.Object {
 	if len(args) != 1 {
 		return newError("wrong number of arguments. got=%d, want=1", len(args))
 	}
 
 	switch arg := args[0].(type) {
-	case *Boolean:
+	case *object.Boolean:
 		if arg.Value {
-			return &Integer{Value: 1}
+			return &object.Integer{Value: 1}
 		}
-		return &Integer{Value: 0}
-	case *Integer:
+		return &object.Integer{Value: 0}
+	case *object.Integer:
 		return arg
-	case *String:
+	case *object.String:
 		n, err := strconv.ParseInt(arg.Value, 10, 64)
 		if err != nil {
 			return newError("could not parse string to int: %s", err)
 		}
 
-		return &Integer{Value: n}
+		return &object.Integer{Value: n}
 	default:
 		return newError("argument to `int` not supported, got=%s", args[0].Type())
 	}
diff --git a/object/builtin_join.go b/builtins/join.go
similarity index 63%
rename from object/builtin_join.go
rename to builtins/join.go
index 0afe533..22b879d 100644
--- a/object/builtin_join.go
+++ b/builtins/join.go
@@ -1,23 +1,25 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import (
 	"strings"
 )
 
 // Join ...
-func Join(args ...Object) Object {
+func Join(args ...object.Object) object.Object {
 	if len(args) != 2 {
 		return newError("wrong number of arguments. got=%d, want=1",
 			len(args))
 	}
 
-	if arr, ok := args[0].(*Array); ok {
-		if sep, ok := args[1].(*String); ok {
+	if arr, ok := args[0].(*object.Array); ok {
+		if sep, ok := args[1].(*object.String); ok {
 			a := make([]string, len(arr.Elements))
 			for i, el := range arr.Elements {
 				a[i] = el.String()
 			}
-			return &String{Value: strings.Join(a, sep.Value)}
+			return &object.String{Value: strings.Join(a, sep.Value)}
 		} else {
 			return newError("expected arg #2 to be `str` got got=%T", args[1])
 		}
diff --git a/object/builtin_last.go b/builtins/last.go
similarity index 64%
rename from object/builtin_last.go
rename to builtins/last.go
index e929d38..c04b1aa 100644
--- a/object/builtin_last.go
+++ b/builtins/last.go
@@ -1,17 +1,19 @@
-package object
+package builtins
+
+import "monkey/object"
 
 // Last ...
-func Last(args ...Object) Object {
+func Last(args ...object.Object) object.Object {
 	if len(args) != 1 {
 		return newError("wrong number of arguments. got=%d, want=1",
 			len(args))
 	}
-	if args[0].Type() != ARRAY_OBJ {
+	if args[0].Type() != object.ARRAY_OBJ {
 		return newError("argument to `last` must be array, got %s",
 			args[0].Type())
 	}
 
-	arr := args[0].(*Array)
+	arr := args[0].(*object.Array)
 	length := len(arr.Elements)
 	if length > 0 {
 		return arr.Elements[length-1]
diff --git a/object/builtin_len.go b/builtins/len.go
similarity index 50%
rename from object/builtin_len.go
rename to builtins/len.go
index 1813290..03c9667 100644
--- a/object/builtin_len.go
+++ b/builtins/len.go
@@ -1,19 +1,21 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import "unicode/utf8"
 
 // Len ...
-func Len(args ...Object) Object {
+func Len(args ...object.Object) object.Object {
 	if len(args) != 1 {
 		return newError("wrong number of arguments. got=%d, want=1",
 			len(args))
 	}
 
 	switch arg := args[0].(type) {
-	case *Array:
-		return &Integer{Value: int64(len(arg.Elements))}
-	case *String:
-		return &Integer{Value: int64(utf8.RuneCountInString(arg.Value))}
+	case *object.Array:
+		return &object.Integer{Value: int64(len(arg.Elements))}
+	case *object.String:
+		return &object.Integer{Value: int64(utf8.RuneCountInString(arg.Value))}
 	default:
 		return newError("argument to `len` not supported, got %s",
 			args[0].Type())
diff --git a/object/builtin_lower.go b/builtins/lower.go
similarity index 51%
rename from object/builtin_lower.go
rename to builtins/lower.go
index be41ac2..de8babf 100644
--- a/object/builtin_lower.go
+++ b/builtins/lower.go
@@ -1,16 +1,18 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import "strings"
 
 // Lower ...
-func Lower(args ...Object) Object {
+func Lower(args ...object.Object) object.Object {
 	if len(args) != 1 {
 		return newError("wrong number of arguments. got=%d, want=1",
 			len(args))
 	}
 
-	if str, ok := args[0].(*String); ok {
-		return &String{Value: strings.ToLower(str.Value)}
+	if str, ok := args[0].(*object.String); ok {
+		return &object.String{Value: strings.ToLower(str.Value)}
 	}
 	return newError("expected `str` argument to `lower` got=%T", args[0])
 }
diff --git a/object/builtin_pop.go b/builtins/pop.go
similarity index 70%
rename from object/builtin_pop.go
rename to builtins/pop.go
index 3710c24..cbfaab6 100644
--- a/object/builtin_pop.go
+++ b/builtins/pop.go
@@ -1,17 +1,19 @@
-package object
+package builtins
+
+import "monkey/object"
 
 // Pop ...
-func Pop(args ...Object) Object {
+func Pop(args ...object.Object) object.Object {
 	if len(args) != 1 {
 		return newError("wrong number of arguments. got=%d, want=1",
 			len(args))
 	}
-	if args[0].Type() != ARRAY_OBJ {
+	if args[0].Type() != object.ARRAY_OBJ {
 		return newError("argument to `pop` must be array, got %s",
 			args[0].Type())
 	}
 
-	arr := args[0].(*Array)
+	arr := args[0].(*object.Array)
 	length := len(arr.Elements)
 
 	if length == 0 {
diff --git a/object/builtin_print.go b/builtins/print.go
similarity index 52%
rename from object/builtin_print.go
rename to builtins/print.go
index c1250a5..6a4257e 100644
--- a/object/builtin_print.go
+++ b/builtins/print.go
@@ -1,9 +1,11 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import "fmt"
 
 // Print ...
-func Print(args ...Object) Object {
+func Print(args ...object.Object) object.Object {
 	for _, arg := range args {
 		fmt.Println(arg.String())
 	}
diff --git a/object/builtin_push.go b/builtins/push.go
similarity index 53%
rename from object/builtin_push.go
rename to builtins/push.go
index 22691cb..9e7b93e 100644
--- a/object/builtin_push.go
+++ b/builtins/push.go
@@ -1,26 +1,28 @@
-package object
+package builtins
+
+import "monkey/object"
 
 // Push ...
-func Push(args ...Object) Object {
+func Push(args ...object.Object) object.Object {
 	if len(args) != 2 {
 		return newError("wrong number of arguments. got=%d, want=2",
 			len(args))
 	}
-	if args[0].Type() != ARRAY_OBJ {
+	if args[0].Type() != object.ARRAY_OBJ {
 		return newError("argument to `push` must be array, got %s",
 			args[0].Type())
 	}
 
-	arr := args[0].(*Array)
+	arr := args[0].(*object.Array)
 	length := len(arr.Elements)
 
-	newElements := make([]Object, length+1)
+	newElements := make([]object.Object, length+1)
 	copy(newElements, arr.Elements)
-	if immutable, ok := args[1].(Immutable); ok {
+	if immutable, ok := args[1].(object.Immutable); ok {
 		newElements[length] = immutable.Clone()
 	} else {
 		newElements[length] = args[1]
 	}
 
-	return &Array{Elements: newElements}
+	return &object.Array{Elements: newElements}
 }
diff --git a/object/builtin_read.go b/builtins/read.go
similarity index 67%
rename from object/builtin_read.go
rename to builtins/read.go
index 9386d1b..b996025 100644
--- a/object/builtin_read.go
+++ b/builtins/read.go
@@ -1,17 +1,19 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import (
 	"os"
 )
 
 // Read ...
-func Read(args ...Object) Object {
+func Read(args ...object.Object) object.Object {
 	if len(args) != 1 {
 		return newError("wrong number of arguments. got=%d, want=1",
 			len(args))
 	}
 
-	arg, ok := args[0].(*String)
+	arg, ok := args[0].(*object.String)
 	if !ok {
 		return newError("argument to `read` expected to be `str` got=%T", args[0].Type())
 	}
@@ -22,5 +24,5 @@ func Read(args ...Object) Object {
 		return newError("error reading file: %s", err)
 	}
 
-	return &String{Value: string(data)}
+	return &object.String{Value: string(data)}
 }
diff --git a/object/builtin_rest.go b/builtins/rest.go
similarity index 53%
rename from object/builtin_rest.go
rename to builtins/rest.go
index 9a8b584..15f730a 100644
--- a/object/builtin_rest.go
+++ b/builtins/rest.go
@@ -1,22 +1,24 @@
-package object
+package builtins
+
+import "monkey/object"
 
 // Rest ...
-func Rest(args ...Object) Object {
+func Rest(args ...object.Object) object.Object {
 	if len(args) != 1 {
 		return newError("wrong number of arguments. got=%d, want=1",
 			len(args))
 	}
-	if args[0].Type() != ARRAY_OBJ {
+	if args[0].Type() != object.ARRAY_OBJ {
 		return newError("argument to `rest` must be array, got %s",
 			args[0].Type())
 	}
 
-	arr := args[0].(*Array)
+	arr := args[0].(*object.Array)
 	length := len(arr.Elements)
 	if length > 0 {
-		newElements := make([]Object, length-1, length-1)
+		newElements := make([]object.Object, length-1, length-1)
 		copy(newElements, arr.Elements[1:length])
-		return &Array{Elements: newElements}
+		return &object.Array{Elements: newElements}
 	}
 
 	return nil
diff --git a/object/builtin_split.go b/builtins/split.go
similarity index 58%
rename from object/builtin_split.go
rename to builtins/split.go
index 566eb1a..fb05c76 100644
--- a/object/builtin_split.go
+++ b/builtins/split.go
@@ -1,23 +1,25 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import (
 	"strings"
 )
 
 // Split ...
-func Split(args ...Object) Object {
+func Split(args ...object.Object) object.Object {
 	if len(args) < 1 {
 		return newError("wrong number of arguments. got=%d, want=1",
 			len(args))
 	}
 
-	if obj, ok := args[0].(*String); ok {
+	if obj, ok := args[0].(*object.String); ok {
 		var sep string
 
 		s := obj.Value
 
 		if len(args) == 2 {
-			if obj, ok := args[1].(*String); ok {
+			if obj, ok := args[1].(*object.String); ok {
 				sep = obj.Value
 			} else {
 				return newError("expected arg #2 to be `str` got=%T", args[1])
@@ -25,11 +27,11 @@ func Split(args ...Object) Object {
 		}
 
 		tokens := strings.Split(s, sep)
-		elements := make([]Object, len(tokens))
+		elements := make([]object.Object, len(tokens))
 		for i, token := range tokens {
-			elements[i] = &String{Value: token}
+			elements[i] = &object.String{Value: token}
 		}
-		return &Array{Elements: elements}
+		return &object.Array{Elements: elements}
 	} else {
 		return newError("expected arg #1 to be `str` got got=%T", args[0])
 	}
diff --git a/object/builtin_str.go b/builtins/str.go
similarity index 65%
rename from object/builtin_str.go
rename to builtins/str.go
index cc33298..8c77a8f 100644
--- a/object/builtin_str.go
+++ b/builtins/str.go
@@ -1,11 +1,13 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import (
 	"fmt"
 )
 
 // Str ...
-func Str(args ...Object) Object {
+func Str(args ...object.Object) object.Object {
 	if len(args) != 1 {
 		return newError("wrong number of arguments. got=%d, want=1", len(args))
 	}
@@ -15,5 +17,5 @@ func Str(args ...Object) Object {
 		return newError("argument to `str` not supported, got %s", args[0].Type())
 	}
 
-	return &String{Value: arg.String()}
+	return &object.String{Value: arg.String()}
 }
diff --git a/builtins/typeof.go b/builtins/typeof.go
new file mode 100644
index 0000000..c093254
--- /dev/null
+++ b/builtins/typeof.go
@@ -0,0 +1,12 @@
+package builtins
+
+import "monkey/object"
+
+// TypeOf  ...
+func TypeOf(args ...object.Object) object.Object {
+	if len(args) != 1 {
+		return newError("wrong number of arguments. got=%d, want=1", len(args))
+	}
+
+	return &object.String{Value: string(args[0].Type())}
+}
diff --git a/object/builtin_upper.go b/builtins/upper.go
similarity index 51%
rename from object/builtin_upper.go
rename to builtins/upper.go
index b1e9e5f..45c0880 100644
--- a/object/builtin_upper.go
+++ b/builtins/upper.go
@@ -1,16 +1,18 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import "strings"
 
 // Upper ...
-func Upper(args ...Object) Object {
+func Upper(args ...object.Object) object.Object {
 	if len(args) != 1 {
 		return newError("wrong number of arguments. got=%d, want=1",
 			len(args))
 	}
 
-	if str, ok := args[0].(*String); ok {
-		return &String{Value: strings.ToUpper(str.Value)}
+	if str, ok := args[0].(*object.String); ok {
+		return &object.String{Value: strings.ToUpper(str.Value)}
 	}
 	return newError("expected `str` argument to `upper` got=%T", args[0])
 }
diff --git a/object/builtin_write.go b/builtins/write.go
similarity index 72%
rename from object/builtin_write.go
rename to builtins/write.go
index 2e1eb6a..c2ff56f 100644
--- a/object/builtin_write.go
+++ b/builtins/write.go
@@ -1,23 +1,25 @@
-package object
+package builtins
+
+import "monkey/object"
 
 import (
 	"os"
 )
 
 // Write ...
-func Write(args ...Object) Object {
+func Write(args ...object.Object) object.Object {
 	if len(args) != 2 {
 		return newError("wrong number of arguments. got=%d, want=2",
 			len(args))
 	}
 
-	arg, ok := args[0].(*String)
+	arg, ok := args[0].(*object.String)
 	if !ok {
 		return newError("argument #1 to `write` expected to be `str` got=%T", args[0].Type())
 	}
 	filename := arg.Value
 
-	arg, ok = args[1].(*String)
+	arg, ok = args[1].(*object.String)
 	if !ok {
 		return newError("argument #2 to `write` expected to be `str` got=%T", args[1].Type())
 	}
@@ -28,5 +30,5 @@ func Write(args ...Object) Object {
 		return newError("error writing file: %s", err)
 	}
 
-	return &Null{}
+	return &object.Null{}
 }
diff --git a/compiler/compiler.go b/compiler/compiler.go
index 1382f4f..f3b823b 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"log"
 	"monkey/ast"
+	"monkey/builtins"
 	"monkey/code"
 	"monkey/object"
 	"sort"
@@ -42,7 +43,7 @@ func New() *Compiler {
 
 	symbolTable := NewSymbolTable()
 
-	for i, builtin := range object.BuiltinsIndex {
+	for i, builtin := range builtins.BuiltinsIndex {
 		symbolTable.DefineBuiltin(i, builtin.Name)
 	}
 
diff --git a/compiler/compiler_test.go b/compiler/compiler_test.go
index a725f0c..cc920dc 100644
--- a/compiler/compiler_test.go
+++ b/compiler/compiler_test.go
@@ -879,11 +879,11 @@ func TestBuiltins(t *testing.T) {
             `,
 			expectedConstants: []interface{}{1},
 			expectedInstructions: []code.Instructions{
-				code.Make(code.OpGetBuiltin, 10),
+				code.Make(code.OpGetBuiltin, 11),
 				code.Make(code.OpArray, 0),
 				code.Make(code.OpCall, 1),
 				code.Make(code.OpPop),
-				code.Make(code.OpGetBuiltin, 14),
+				code.Make(code.OpGetBuiltin, 15),
 				code.Make(code.OpArray, 0),
 				code.Make(code.OpConstant, 0),
 				code.Make(code.OpCall, 2),
@@ -894,7 +894,7 @@ func TestBuiltins(t *testing.T) {
 			input: `fn() { return len([]) }`,
 			expectedConstants: []interface{}{
 				[]code.Instructions{
-					code.Make(code.OpGetBuiltin, 10),
+					code.Make(code.OpGetBuiltin, 11),
 					code.Make(code.OpArray, 0),
 					code.Make(code.OpCall, 1),
 					code.Make(code.OpReturn),
diff --git a/evaluator/builtins.go b/evaluator/builtins.go
deleted file mode 100644
index a9db8f9..0000000
--- a/evaluator/builtins.go
+++ /dev/null
@@ -1,7 +0,0 @@
-package evaluator
-
-import (
-	"monkey/object"
-)
-
-var builtins = object.Builtins
diff --git a/evaluator/evaluator.go b/evaluator/evaluator.go
index 63a1e60..a4c27eb 100644
--- a/evaluator/evaluator.go
+++ b/evaluator/evaluator.go
@@ -3,6 +3,7 @@ package evaluator
 import (
 	"fmt"
 	"monkey/ast"
+	"monkey/builtins"
 	"monkey/object"
 	"strings"
 )
@@ -487,7 +488,7 @@ func evalIdentifier(node *ast.Identifier, env *object.Environment) object.Object
 		return val
 	}
 
-	if builtin, ok := builtins[node.Value]; ok {
+	if builtin, ok := builtins.Builtins[node.Value]; ok {
 		return builtin
 	}
 
diff --git a/object/array.go b/object/array.go
new file mode 100644
index 0000000..48adf00
--- /dev/null
+++ b/object/array.go
@@ -0,0 +1,51 @@
+package object
+
+import (
+	"bytes"
+	"strings"
+)
+
+// Array is the array literal type that holds a slice of Object(s)
+type Array struct {
+	Elements []Object
+}
+
+func (ao *Array) Type() ObjectType {
+	return ARRAY_OBJ
+}
+func (ao *Array) Inspect() string {
+	var out bytes.Buffer
+
+	var elements []string
+	for _, e := range ao.Elements {
+		elements = append(elements, e.Inspect())
+	}
+
+	out.WriteString("[")
+	out.WriteString(strings.Join(elements, ", "))
+	out.WriteString("]")
+
+	return out.String()
+}
+func (ao *Array) String() string {
+	return ao.Inspect()
+}
+func (ao *Array) Equal(other Object) bool {
+	if obj, ok := other.(*Array); ok {
+		if len(ao.Elements) != len(obj.Elements) {
+			return false
+		}
+		for i, el := range ao.Elements {
+			cmp, ok := el.(Comparable)
+			if !ok {
+				return false
+			}
+			if !cmp.Equal(obj.Elements[i]) {
+				return false
+			}
+		}
+
+		return true
+	}
+	return false
+}
diff --git a/object/bool.go b/object/bool.go
new file mode 100644
index 0000000..55fc12d
--- /dev/null
+++ b/object/bool.go
@@ -0,0 +1,28 @@
+package object
+
+import (
+	"fmt"
+)
+
+type Boolean struct {
+	Value bool
+}
+
+func (b *Boolean) Type() ObjectType {
+	return BOOLEAN_OBJ
+}
+func (b *Boolean) Inspect() string {
+	return fmt.Sprintf("%t", b.Value)
+}
+func (b *Boolean) Clone() Object {
+	return &Boolean{Value: b.Value}
+}
+func (b *Boolean) String() string {
+	return b.Inspect()
+}
+func (b *Boolean) Equal(other Object) bool {
+	if obj, ok := other.(*Boolean); ok {
+		return b.Value == obj.Value
+	}
+	return false
+}
diff --git a/object/builtin.go b/object/builtin.go
new file mode 100644
index 0000000..c443ac0
--- /dev/null
+++ b/object/builtin.go
@@ -0,0 +1,18 @@
+package object
+
+import "fmt"
+
+type Builtin struct {
+	Name string
+	Fn   BuiltinFunction
+}
+
+func (b *Builtin) Type() ObjectType {
+	return BUILTIN_OBJ
+}
+func (b *Builtin) Inspect() string {
+	return fmt.Sprintf("<built-in function %s>", b.Name)
+}
+func (b *Builtin) String() string {
+	return b.Inspect()
+}
diff --git a/object/builtin_args.go b/object/builtin_args.go
deleted file mode 100644
index 4e66137..0000000
--- a/object/builtin_args.go
+++ /dev/null
@@ -1,10 +0,0 @@
-package object
-
-// Args  ...
-func Args(args ...Object) Object {
-	elements := make([]Object, len(Arguments))
-	for i, arg := range Arguments {
-		elements[i] = &String{Value: arg}
-	}
-	return &Array{Elements: elements}
-}
diff --git a/object/builtin_bool.go b/object/builtin_bool.go
deleted file mode 100644
index 2874d2e..0000000
--- a/object/builtin_bool.go
+++ /dev/null
@@ -1,38 +0,0 @@
-package object
-
-// Bool ...
-func Bool(args ...Object) Object {
-	if len(args) != 1 {
-		return newError("wrong number of arguments. got=%d, want=1", len(args))
-	}
-
-	switch arg := args[0].(type) {
-	case *Null:
-		return &Boolean{Value: false}
-	case *Boolean:
-		return arg
-	case *Integer:
-		if arg.Value == 0 {
-			return &Boolean{Value: false}
-		}
-		return &Boolean{Value: true}
-	case *String:
-		if len(arg.Value) > 0 {
-			return &Boolean{Value: true}
-		}
-		return &Boolean{Value: false}
-	case *Array:
-		if len(arg.Elements) > 0 {
-			return &Boolean{Value: true}
-		}
-		return &Boolean{Value: false}
-	case *Hash:
-		if len(arg.Pairs) > 0 {
-			return &Boolean{Value: true}
-		}
-		return &Boolean{Value: false}
-
-	default:
-		return newError("argument to `bool` not supported, got=%s", args[0].Type())
-	}
-}
diff --git a/object/builtin_exit.go b/object/builtin_exit.go
deleted file mode 100644
index d9502e3..0000000
--- a/object/builtin_exit.go
+++ /dev/null
@@ -1,17 +0,0 @@
-package object
-
-// Exit ...
-func Exit(args ...Object) Object {
-	var status int
-	if len(args) == 1 {
-		if args[0].Type() != INTEGER_OBJ {
-			return newError("argument to `exit` must be INTEGER, got %s",
-				args[0].Type())
-		}
-		status = int(args[0].(*Integer).Value)
-	}
-
-	ExitFunction(status)
-
-	return nil
-}
diff --git a/object/builtin_typeof.go b/object/builtin_typeof.go
deleted file mode 100644
index 6382e53..0000000
--- a/object/builtin_typeof.go
+++ /dev/null
@@ -1,10 +0,0 @@
-package object
-
-// TypeOf  ...
-func TypeOf(args ...Object) Object {
-	if len(args) != 1 {
-		return newError("wrong number of arguments. got=%d, want=1", len(args))
-	}
-
-	return &String{Value: string(args[0].Type())}
-}
diff --git a/object/closure.go b/object/closure.go
new file mode 100644
index 0000000..3375539
--- /dev/null
+++ b/object/closure.go
@@ -0,0 +1,37 @@
+package object
+
+import (
+	"fmt"
+	"monkey/code"
+)
+
+type CompiledFunction struct {
+	Instructions  code.Instructions
+	NumLocals     int
+	NumParameters int
+}
+
+func (cf *CompiledFunction) Type() ObjectType {
+	return COMPILED_FUNCTION_OBJ
+}
+func (cf *CompiledFunction) Inspect() string {
+	return fmt.Sprintf("CompiledFunction[%p]", cf)
+}
+func (cf *CompiledFunction) String() string {
+	return cf.Inspect()
+}
+
+type Closure struct {
+	Fn   *CompiledFunction
+	Free []Object
+}
+
+func (c *Closure) Type() ObjectType {
+	return CLOSURE_OBJ
+}
+func (c *Closure) Inspect() string {
+	return fmt.Sprintf("Closure[%p]", c)
+}
+func (c *Closure) String() string {
+	return c.Inspect()
+}
diff --git a/object/error.go b/object/error.go
new file mode 100644
index 0000000..d50e0b1
--- /dev/null
+++ b/object/error.go
@@ -0,0 +1,18 @@
+package object
+
+type Error struct {
+	Message string
+}
+
+func (e *Error) Type() ObjectType {
+	return ERROR_OBJ
+}
+func (e *Error) Inspect() string {
+	return "Error: " + e.Message
+}
+func (e *Error) Clone() Object {
+	return &Error{Message: e.Message}
+}
+func (e *Error) String() string {
+	return e.Message
+}
diff --git a/object/function.go b/object/function.go
new file mode 100644
index 0000000..7677e95
--- /dev/null
+++ b/object/function.go
@@ -0,0 +1,51 @@
+package object
+
+import (
+	"bytes"
+	"monkey/ast"
+	"strings"
+)
+
+type Function struct {
+	Parameters []*ast.Identifier
+	Body       *ast.BlockStatement
+	Env        *Environment
+}
+
+func (f *Function) Type() ObjectType {
+	return FUNCTION_OBJ
+}
+func (f *Function) Inspect() string {
+	var out bytes.Buffer
+
+	params := []string{}
+	for _, p := range f.Parameters {
+		params = append(params, p.String())
+	}
+
+	out.WriteString("fn")
+	out.WriteString("(")
+	out.WriteString(strings.Join(params, ", "))
+	out.WriteString(") {\n")
+	out.WriteString(f.Body.String())
+	out.WriteString("\n}")
+
+	return out.String()
+}
+func (f *Function) String() string {
+	return f.Inspect()
+}
+
+type ReturnValue struct {
+	Value Object
+}
+
+func (rv *ReturnValue) Type() ObjectType {
+	return RETURN_VALUE_OBJ
+}
+func (rv *ReturnValue) Inspect() string {
+	return rv.Value.Inspect()
+}
+func (rv *ReturnValue) String() string {
+	return rv.Inspect()
+}
diff --git a/object/hash.go b/object/hash.go
new file mode 100644
index 0000000..b0b420c
--- /dev/null
+++ b/object/hash.go
@@ -0,0 +1,91 @@
+package object
+
+import (
+	"bytes"
+	"fmt"
+	"hash/fnv"
+	"strings"
+)
+
+type HashKey struct {
+	Type  ObjectType
+	Value uint64
+}
+
+func (b *Boolean) HashKey() HashKey {
+	var value uint64
+
+	if b.Value {
+		value = 1
+	} else {
+		value = 0
+	}
+
+	return HashKey{Type: b.Type(), Value: value}
+}
+
+func (i *Integer) HashKey() HashKey {
+	return HashKey{Type: i.Type(), Value: uint64(i.Value)}
+}
+
+func (s *String) HashKey() HashKey {
+	h := fnv.New64a()
+	h.Write([]byte(s.Value))
+
+	return HashKey{Type: s.Type(), Value: h.Sum64()}
+}
+
+type HashPair struct {
+	Key   Object
+	Value Object
+}
+
+type Hash struct {
+	Pairs map[HashKey]HashPair
+}
+
+func (h *Hash) Type() ObjectType {
+	return HASH_OBJ
+}
+func (h *Hash) Inspect() string {
+	var out bytes.Buffer
+
+	pairs := []string{}
+	for _, pair := range h.Pairs {
+		pairs = append(pairs, fmt.Sprintf("%s: %s", pair.Key.Inspect(), pair.Value.Inspect()))
+	}
+
+	out.WriteString("{")
+	out.WriteString(strings.Join(pairs, ", "))
+	out.WriteString("}")
+
+	return out.String()
+}
+func (h *Hash) String() string {
+	return h.Inspect()
+}
+func (h *Hash) Equal(other Object) bool {
+	if obj, ok := other.(*Hash); ok {
+		if len(h.Pairs) != len(obj.Pairs) {
+			return false
+		}
+		for _, pair := range h.Pairs {
+			left := pair.Value
+			hashed := left.(Hashable)
+			right, ok := obj.Pairs[hashed.HashKey()]
+			if !ok {
+				return false
+			}
+			cmp, ok := left.(Comparable)
+			if !ok {
+				return false
+			}
+			if !cmp.Equal(right.Value) {
+				return false
+			}
+		}
+
+		return true
+	}
+	return false
+}
diff --git a/object/int.go b/object/int.go
new file mode 100644
index 0000000..fdd7354
--- /dev/null
+++ b/object/int.go
@@ -0,0 +1,26 @@
+package object
+
+import "fmt"
+
+type Integer struct {
+	Value int64
+}
+
+func (i *Integer) Type() ObjectType {
+	return INTEGER_OBJ
+}
+func (i *Integer) Inspect() string {
+	return fmt.Sprintf("%d", i.Value)
+}
+func (i *Integer) Clone() Object {
+	return &Integer{Value: i.Value}
+}
+func (i *Integer) String() string {
+	return i.Inspect()
+}
+func (i *Integer) Equal(other Object) bool {
+	if obj, ok := other.(*Integer); ok {
+		return i.Value == obj.Value
+	}
+	return false
+}
diff --git a/object/null.go b/object/null.go
new file mode 100644
index 0000000..e693fea
--- /dev/null
+++ b/object/null.go
@@ -0,0 +1,17 @@
+package object
+
+type Null struct{}
+
+func (n *Null) Type() ObjectType {
+	return NULL_OBJ
+}
+func (n *Null) Inspect() string {
+	return "null"
+}
+func (n *Null) String() string {
+	return n.Inspect()
+}
+func (n *Null) Equal(other Object) bool {
+	_, ok := other.(*Null)
+	return ok
+}
diff --git a/object/object.go b/object/object.go
index 53ef9e3..a58c931 100644
--- a/object/object.go
+++ b/object/object.go
@@ -1,14 +1,6 @@
 package object
 
-import (
-	"bytes"
-	"fmt"
-	"hash/fnv"
-	"monkey/ast"
-	"monkey/code"
-	"strings"
-)
-
+// Type represents the type of an object
 type ObjectType string
 
 const (
@@ -39,333 +31,19 @@ type Immutable interface {
 	Clone() Object
 }
 
+// Object represents a value and implementations are expected to implement
+// `Type()` and `Inspect()` functions
 type Object interface {
 	Type() ObjectType
 	String() string
 	Inspect() string
 }
 
-type Integer struct {
-	Value int64
-}
-
-type CompiledFunction struct {
-	Instructions  code.Instructions
-	NumLocals     int
-	NumParameters int
-}
-
-func (i *Integer) Type() ObjectType {
-	return INTEGER_OBJ
-}
-func (i *Integer) Inspect() string {
-	return fmt.Sprintf("%d", i.Value)
-}
-func (i *Integer) Clone() Object {
-	return &Integer{Value: i.Value}
-}
-func (i *Integer) String() string {
-	return i.Inspect()
-}
-func (i *Integer) Equal(other Object) bool {
-	if obj, ok := other.(*Integer); ok {
-		return i.Value == obj.Value
-	}
-	return false
-}
-
-type Boolean struct {
-	Value bool
-}
-
-func (b *Boolean) Type() ObjectType {
-	return BOOLEAN_OBJ
-}
-func (b *Boolean) Inspect() string {
-	return fmt.Sprintf("%t", b.Value)
-}
-func (b *Boolean) Clone() Object {
-	return &Boolean{Value: b.Value}
-}
-func (b *Boolean) String() string {
-	return b.Inspect()
-}
-func (b *Boolean) Equal(other Object) bool {
-	if obj, ok := other.(*Boolean); ok {
-		return b.Value == obj.Value
-	}
-	return false
-}
-
-type Null struct{}
-
-func (n *Null) Type() ObjectType {
-	return NULL_OBJ
-}
-func (n *Null) Inspect() string {
-	return "null"
-}
-func (n *Null) String() string {
-	return n.Inspect()
-}
-func (n *Null) Equal(other Object) bool {
-	_, ok := other.(*Null)
-	return ok
-}
-
-type ReturnValue struct {
-	Value Object
-}
-
-func (rv *ReturnValue) Type() ObjectType {
-	return RETURN_VALUE_OBJ
-}
-func (rv *ReturnValue) Inspect() string {
-	return rv.Value.Inspect()
-}
-func (rv *ReturnValue) String() string {
-	return rv.Inspect()
-}
-
-type Error struct {
-	Message string
-}
-
-func (e *Error) Type() ObjectType {
-	return ERROR_OBJ
-}
-func (e *Error) Inspect() string {
-	return "Error: " + e.Message
-}
-func (e *Error) Clone() Object {
-	return &Error{Message: e.Message}
-}
-func (e *Error) String() string {
-	return e.Message
-}
-
-type Function struct {
-	Parameters []*ast.Identifier
-	Body       *ast.BlockStatement
-	Env        *Environment
-}
-
-func (f *Function) Type() ObjectType {
-	return FUNCTION_OBJ
-}
-func (f *Function) Inspect() string {
-	var out bytes.Buffer
-
-	params := []string{}
-	for _, p := range f.Parameters {
-		params = append(params, p.String())
-	}
-
-	out.WriteString("fn")
-	out.WriteString("(")
-	out.WriteString(strings.Join(params, ", "))
-	out.WriteString(") {\n")
-	out.WriteString(f.Body.String())
-	out.WriteString("\n}")
-
-	return out.String()
-}
-func (f *Function) String() string {
-	return f.Inspect()
-}
-
-type String struct {
-	Value string
-}
-
-func (s *String) Type() ObjectType {
-	return STRING_OBJ
-}
-func (s *String) Inspect() string {
-	return fmt.Sprintf("%#v", s.Value)
-}
-func (s *String) Clone() Object {
-	return &String{Value: s.Value}
-}
-func (s *String) String() string {
-	return s.Value
-}
-func (s *String) Equal(other Object) bool {
-	if obj, ok := other.(*String); ok {
-		return s.Value == obj.Value
-	}
-	return false
-}
-
-type BuiltinFunction func(args ...Object) Object
-
-type Builtin struct {
-	Name string
-	Fn   BuiltinFunction
-}
-
-func (b *Builtin) Type() ObjectType {
-	return BUILTIN_OBJ
-}
-func (b *Builtin) Inspect() string {
-	return fmt.Sprintf("<built-in function %s>", b.Name)
-}
-func (b *Builtin) String() string {
-	return b.Inspect()
-}
-
-type Array struct {
-	Elements []Object
-}
-
-func (ao *Array) Type() ObjectType {
-	return ARRAY_OBJ
-}
-func (ao *Array) Inspect() string {
-	var out bytes.Buffer
-
-	elements := []string{}
-	for _, e := range ao.Elements {
-		elements = append(elements, e.Inspect())
-	}
-
-	out.WriteString("[")
-	out.WriteString(strings.Join(elements, ", "))
-	out.WriteString("]")
-
-	return out.String()
-}
-func (ao *Array) String() string {
-	return ao.Inspect()
-}
-func (ao *Array) Equal(other Object) bool {
-	if obj, ok := other.(*Array); ok {
-		if len(ao.Elements) != len(obj.Elements) {
-			return false
-		}
-		for i, el := range ao.Elements {
-			cmp, ok := el.(Comparable)
-			if !ok {
-				return false
-			}
-			if !cmp.Equal(obj.Elements[i]) {
-				return false
-			}
-		}
-
-		return true
-	}
-	return false
-}
-
-type HashKey struct {
-	Type  ObjectType
-	Value uint64
-}
-
-func (b *Boolean) HashKey() HashKey {
-	var value uint64
-
-	if b.Value {
-		value = 1
-	} else {
-		value = 0
-	}
-
-	return HashKey{Type: b.Type(), Value: value}
-}
-
+// Hashable is the interface for all hashable objects which must implement
+// the HashKey() method which returns a HashKey result.
 type Hashable interface {
 	HashKey() HashKey
 }
 
-func (i *Integer) HashKey() HashKey {
-	return HashKey{Type: i.Type(), Value: uint64(i.Value)}
-}
-
-func (s *String) HashKey() HashKey {
-	h := fnv.New64a()
-	h.Write([]byte(s.Value))
-
-	return HashKey{Type: s.Type(), Value: h.Sum64()}
-}
-
-type HashPair struct {
-	Key   Object
-	Value Object
-}
-
-type Hash struct {
-	Pairs map[HashKey]HashPair
-}
-
-func (h *Hash) Type() ObjectType {
-	return HASH_OBJ
-}
-func (h *Hash) Inspect() string {
-	var out bytes.Buffer
-
-	pairs := []string{}
-	for _, pair := range h.Pairs {
-		pairs = append(pairs, fmt.Sprintf("%s: %s", pair.Key.Inspect(), pair.Value.Inspect()))
-	}
-
-	out.WriteString("{")
-	out.WriteString(strings.Join(pairs, ", "))
-	out.WriteString("}")
-
-	return out.String()
-}
-func (h *Hash) String() string {
-	return h.Inspect()
-}
-func (h *Hash) Equal(other Object) bool {
-	if obj, ok := other.(*Hash); ok {
-		if len(h.Pairs) != len(obj.Pairs) {
-			return false
-		}
-		for _, pair := range h.Pairs {
-			left := pair.Value
-			hashed := left.(Hashable)
-			right, ok := obj.Pairs[hashed.HashKey()]
-			if !ok {
-				return false
-			}
-			cmp, ok := left.(Comparable)
-			if !ok {
-				return false
-			}
-			if !cmp.Equal(right.Value) {
-				return false
-			}
-		}
-
-		return true
-	}
-	return false
-}
-
-func (cf *CompiledFunction) Type() ObjectType {
-	return COMPILED_FUNCTION_OBJ
-}
-func (cf *CompiledFunction) Inspect() string {
-	return fmt.Sprintf("CompiledFunction[%p]", cf)
-}
-func (cf *CompiledFunction) String() string {
-	return cf.Inspect()
-}
-
-type Closure struct {
-	Fn   *CompiledFunction
-	Free []Object
-}
-
-func (c *Closure) Type() ObjectType {
-	return CLOSURE_OBJ
-}
-func (c *Closure) Inspect() string {
-	return fmt.Sprintf("Closure[%p]", c)
-}
-func (c *Closure) String() string {
-	return c.Inspect()
-}
+// BuiltinFunction represents the builtin function type
+type BuiltinFunction func(args ...Object) Object
diff --git a/object/str.go b/object/str.go
new file mode 100644
index 0000000..815903d
--- /dev/null
+++ b/object/str.go
@@ -0,0 +1,26 @@
+package object
+
+import "fmt"
+
+type String struct {
+	Value string
+}
+
+func (s *String) Type() ObjectType {
+	return STRING_OBJ
+}
+func (s *String) Inspect() string {
+	return fmt.Sprintf("%#v", s.Value)
+}
+func (s *String) Clone() Object {
+	return &String{Value: s.Value}
+}
+func (s *String) String() string {
+	return s.Value
+}
+func (s *String) Equal(other Object) bool {
+	if obj, ok := other.(*String); ok {
+		return s.Value == obj.Value
+	}
+	return false
+}
diff --git a/plugins/hello.go b/plugins/hello.go
new file mode 100644
index 0000000..0360bea
--- /dev/null
+++ b/plugins/hello.go
@@ -0,0 +1,8 @@
+package main
+
+import "monkey/object"
+
+// Hello ...
+func Hello(args ...object.Object) object.Object {
+	return &object.String{Value: "Hello World!"}
+}
diff --git a/repl/repl.go b/repl/repl.go
index f9228cf..e3876e8 100644
--- a/repl/repl.go
+++ b/repl/repl.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"log"
+	"monkey/builtins"
 	"monkey/compiler"
 	"monkey/evaluator"
 	"monkey/lexer"
@@ -49,7 +50,7 @@ type VMState struct {
 
 func NewVMState() *VMState {
 	symbolTable := compiler.NewSymbolTable()
-	for i, builtin := range object.BuiltinsIndex {
+	for i, builtin := range builtins.BuiltinsIndex {
 		symbolTable.DefineBuiltin(i, builtin.Name)
 	}
 
diff --git a/vm/vm.go b/vm/vm.go
index d989ab0..d1a9841 100644
--- a/vm/vm.go
+++ b/vm/vm.go
@@ -3,6 +3,7 @@ package vm
 import (
 	"fmt"
 	"log"
+	"monkey/builtins"
 	"monkey/code"
 	"monkey/compiler"
 	"monkey/object"
@@ -323,7 +324,7 @@ func (vm *VM) Run() error {
 			builtinIndex := code.ReadUint8(ins[ip+1:])
 			vm.currentFrame().ip += 1
 
-			builtin := object.BuiltinsIndex[builtinIndex]
+			builtin := builtins.BuiltinsIndex[builtinIndex]
 
 			err := vm.push(builtin)
 			if err != nil {