(assert
  (eq (do
        x = 1
        y = 2
        (add x y))
      3))

(assert
  (eq (do
        (x) = 1
        (y) = 2
        (add (x) (y)))
      3))

(assert
  (eq (do
        (id x) = x
        (add (id 1) (id 2)))
      3))