diff --git a/src/jasinta.py b/src/jasinta.py
--- a/src/jasinta.py
+++ b/src/jasinta.py
@@ -1,4 +1,4 @@
-from std import lib as stdlib, Number
+from std import lib as stdlib, Number, String
 
 
 class Undefined:
@@ -12,6 +12,9 @@ def evaluate(node, context):
 	node_type = node["type"]
 	# retrieve an already existing object from the context
 	if node_type == "Identifier":
+		if hasattr(context[-1], node["name"]):
+			return getattr(context[-1], node["name"])
+
 		for ctx in reversed(context):
 			if node["name"] in ctx:
 				return ctx[node["name"]]
@@ -68,7 +71,10 @@ class AssignmentExpression:
 	def eval(self, context):
 		left = evaluate(self.node["left"], context)
 		right = evaluate(self.node["right"], context)
-		if self.node["operator"] == "+=":
+		op = self.node["operator"]
+		if op == "=":
+			left.val = right.val
+		elif op == "+=":
 			left.val += right.val
 		else:
 			raise NotImplementedError
@@ -84,7 +90,7 @@ class BinaryExpression:
 
 		# in fact this doesn't follow JavaScript "+" semantics
 		if self.node["operator"] == "+":
-			return Number(left.val+right.val)
+			return left+right
 		else:
 			raise NotImplementedError
 
@@ -133,7 +139,7 @@ class Literal:
 			else:
 				return Number(val)
 		else:
-			raise NotImplementedError
+			return String(val)
 
 
 node_index = {cls.__name__: cls for cls in [