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")
; Evaluation aborted on #<ccl::no-such-package #x3020038F870D>.
cl-user> (defpackage "JSOWN" (:use) (:export "VAL"))
#<Package "JSOWN">
cl-user> (load "/tmp/f.lisp")
; Evaluation aborted on #<unbound-variable #x3020039F5F9D>.
cl-user> (defparameter *JS* nil)
*js*
cl-user> (load "/tmp/f.lisp")
; Evaluation aborted on #<ccl::undefined-function-call #x302003A0DCED>.
cl-user> (defun jsown:val (&rest args) nil)
;Compiler warnings :
;   In jsown:val: Unused lexical variable args
jsown:val
cl-user> (load "/tmp/f.lisp")

nilnil
nil
#P"/private/tmp/f.lisp"
cl-user>