(defun invert (x)
    (if (rest x) 
        (append
         (invert (rest x))
         (cons (first x) nil)
        )
        x
    )
)

(setf demolist '(1 2 3 4 5 6 7 8 9 10))

(defun run nil
    (princ "Original List: ")
    (princ demolist)
    (terpri)
    (princ "Inverted List: ")
    (princ (invert demolist))
    (terpri)
)