| code tree old new |
code := 'sampleCode
	| a |
	a := ''This is a pen''.
	^a'.
old := 'a'. new := 'b'.
tree := Parser new parse: code class: UndefinedObject.
(tree instVarNamed: #temporaries) do: [:each |
	each name = old ifTrue: [each key: new; name: new]].
^tree decompileString  "=> 'sampleCode
	| b |
	b := ''This is a pen''.
	^ b' "