;;; 冗長な記法
(mbe-defrules my-push1
  ((newelt place) (setq place (cons newelt place))))
;;; 引数の形式が1つなのでシンプルな記法でよい
(mbe-defrule my-push2 (newelt place)
  (setq place (cons newelt place)))
(let (x y z)
  (push 1 x)                            ; => (1)
  x                                     ; => (1)
  (my-push1 1 y)                        ; => (1)
  y                                     ; => (1)
  (my-push2 1 z)                        ; => (1)
  z                                     ; => (1)
  )