RosettaCodeData/Task/Extend-your-language/Common-Lisp/extend-your-language.lisp

(defmacro if2 (cond1 cond2 both first second &rest neither)
  (let ((res1 (gensym))
        (res2 (gensym)))
    `(let ((,res1 ,cond1)
           (,res2 ,cond2))
       (cond ((and ,res1 ,res2) ,both)
             (,res1             ,first)
             (,res2             ,second)
             (t                 ,@neither)))))