How to use example functions? – Artificial Intelligence

This program was taken from Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp by Peter Norvig, 1992, Morgan Kaufmann Publishers, Inc. If I compile and load it into a debug window, how would I use it?

; This function returns a random element of the list choices
(defun random-elt (choices)
    "Choose an element from a list at random."
;; elt returns the (n + 1)th element of the list choices 
;; random returns a random integer no large than the number of
;;   elements in the list choices
    (elt choices (random (length choices))))

; This function returns a random element of the given set and returns 
; it in a list
(defun one-of (set)
     "Pick one element of set, and make a list of it."
     (list (random-elt set)))

; Define a sentence as a noun-phrase + verb phrase
(defun sentence ()  (append (noun-phrase) (verb-phrase)))

; Define a noun phrase as an article + noun
(defun noun-phrase () (append (Article) (Noun)))

; Define a verb phrase as a verb + a noun phrase
(defun verb-phrase () (append (Verb) (noun-phrase)))

; This function returns a randomly selected article
(defun Article () (one-of '(the a)))

; This function returns a randomly selected noun
(defun Noun () (one-of '(man ball woman table)))

; This function returns a randomly selected verb
(defun Verb () (one-of '(hit took saw liked)))