cl-user> (cat "/tmp/f.lisp")
;; Funciona: retorna o valor correto
(defmacro only (obj val)
  `(jsown:val ,obj ,val))

(pprint (macroexpand-1 '(only *js* "a"))) ; "amor"


;; Erro: usa o valor dentro de um let
(defmacro only-2 (obj val &body body)
  `(let ((val ,(jsown:val obj val)))
     ,@body))

(pprint (macroexpand-1 '(only-2 *js* "a"
                         (format t "~A" val))))

;; The value
;;   *JS*
;; is not of type
;;   LIST
; No value
cl-user> (load "/tmp/f.lisp")

(jsown:val *js* "a")
(let ((val nil)) (format t "~A" val))
#P"/private/tmp/f.lisp"
cl-user>