(defun p-match (p v)
       (cond
         ((eql p '_) nil)
         ((null p) nil)
         ((atom p) (cons p v))
         ((consp p)
          (let ((first (p-match (car p) (car v)))
            (rest  (p-match (cdr p) (cdr v))))
        (unless (listp (cdr p))
          (setf rest (list rest)))
        (if first
            (cons first rest)
            rest)))))