interaction
  (main):Number out
with
    interaction
      (b):Number out
    is
      ((#b) in (`return5`)()=(#b))
    interaction
      ((x:Number in)+(y:Number in)):Number out
    with
      interaction (res):Number out is (#+(x)(y))
    is
      ((res) in (`sum`) ({x:(x),y:(y)}) = (res))
is
  ((b)+(b))