readFn :: VarMap -> [VariableValue] -> IO VarMap
readFn vars [(StrVar "int")] =
    do line <- getLine
       return $ Map.insert "return" (IntVar $ read line) vars
readFn :: VarMap -> [VariableValue] -> IO VarMap
readFn vars [(StrVar "int")] =
    do line <- getLine
       return $ Map.insert "return" (IntVar $ read line) vars
readFn vars [(StrVar "int")] =
    do line <- getLine
       return $ Map.insert "return" (IntVar $ read line) vars