diff --git a/evaluator/evaluator.go b/evaluator/evaluator.go
index f4ffc13..c719cd5 100644
--- a/evaluator/evaluator.go
+++ b/evaluator/evaluator.go
@@ -521,7 +521,7 @@ func evalIndexExpression(node *ast.IndexExpression, left object.Object, index ob
 	switch {
 	case left.Type() == object.STRING_OBJ && index.Type() == object.NUMBER_OBJ:
 		return evalStringIndexExpression(node, left, index)
-	case left.Type() == object.LIST_OBJ && index.Type() == object.NUMBER_OBJ:
+	case left.Type() == object.LIST_OBJ:
 		return evalListIndexExpression(node, left, index)
 	case left.Type() == object.MAP_OBJ:
 		return evalMapIndexExpression(node.Token.Line, left, index)
@@ -707,6 +707,18 @@ func evalForInExpression(fie *ast.ForInExpression, env *object.Environment) obje
 			}
 		}
 
+		return value.NULL
+	case *object.Map:
+		for _, p := range i.Pairs {
+			env.Set(fie.Key, p.Key)
+			env.Set(fie.Value, p.Value)
+			block := Eval(fie.Block, env)
+
+			if error.IsError(block) {
+				return block
+			}
+		}
+
 		return value.NULL
 	default:
 		return error.NewError(fie.Token.Line, error.UnusableForLoop, i.Inspect())
diff --git a/object/object.go b/object/object.go
index f7ca1df..aea753d 100644
--- a/object/object.go
+++ b/object/object.go
@@ -7,6 +7,7 @@ import (
 	"bytes"
 	"fmt"
 	"hash/fnv"
+	"regexp"
 	"strconv"
 	"strings"
 	"unicode/utf8"
@@ -336,12 +337,44 @@ func (rv *ReturnValue) CallMethod(method string, args []Object) Object {
 
 func (s *String) CallMethod(method string, args []Object) Object {
 	switch method {
+	case "matches":
+		matches, err := regexp.Match(s.Value, []byte(args[0].(*String).Value))
+
+		if err != nil {
+			return &Error{Message: err.Error()}
+		}
+
+		return &Boolean{Value: matches}
+	case "find":
+		re := regexp.MustCompile(s.Value)
+
+		found := re.FindStringSubmatch(args[0].(*String).Value)
+
+		if len(found) > 0 {
+			return &String{Value: found[1]}
+		}
+
+		return &String{}
+	case "findAll":
+		re := regexp.MustCompile(s.Value)
+		list := &List{}
+		found := re.FindStringSubmatch(args[0].(*String).Value)
+
+		for _, f := range found {
+			list.Elements = append(list.Elements, &String{Value: f})
+		}
+
+		return list
 	case "endsWith":
 		hasPrefix := strings.HasSuffix(s.Value, args[0].(*String).Value)
 
 		return &Boolean{Value: hasPrefix}
 	case "length":
 		return &Number{Value: decimal.NewFromInt(int64(utf8.RuneCountInString(s.Value)))}
+	case "replace":
+		value := strings.Replace(s.Value, args[0].(*String).Value, args[1].(*String).Value, -1)
+
+		return &String{Value: value}
 	case "split":
 		split := strings.Split(s.Value, args[0].(*String).Value)
 		list := &List{}
diff --git a/utilities/utilities.go b/utilities/utilities.go
index 577ca75..2c05916 100644
--- a/utilities/utilities.go
+++ b/utilities/utilities.go
@@ -74,13 +74,17 @@ func NativeBoolToBooleanObject(input bool) *object.Boolean {
 
 // IsTruthy returns the truthy value of the passed object.
 func IsTruthy(obj object.Object) bool {
-	switch obj {
-	case value.NULL:
-		return false
-	case value.TRUE:
-		return true
-	case value.FALSE:
+	switch obj := obj.(type) {
+	case *object.Null:
 		return false
+	case *object.Boolean:
+		return obj.Value
+	case *object.String:
+		return len(obj.Value) > 0
+	case *object.List:
+		return len(obj.Elements) > 0
+	case *object.Map:
+		return len(obj.Pairs) > 0
 	default:
 		return true
 	}