insertion sort in common lisp

insertion_sort.lisp

(defun insert (item lst &optional (key #'<))
  (if (null lst)
    (list item)
    (if (funcall key item (car lst))
          (cons item lst) 
          (cons (car lst) (insert item (cdr lst) key)))))

(defun insertion-sort (lst &optional (key #'<))
  (if (null lst)
    lst
    (insert (car lst) (insertion-sort (cdr lst) key) key)))

(insertion-sort '(1 4 2 4 5 1 3 0))

Thank you.