;gnu clisp 2.49

(print "Hello, world!")

(defun counter (S a)
    (IF (EQ S NIL)
        0
        (IF (ATOM (CAR S))
            (IF (EQ (CAR S) a)
                (+ 1 (counter (CDR S) a))
                (counter (CDR S) a)
            )
            (+ (counter (CAR S) a) (counter (CDR S) a))
         )
    )
)

(print (counter `(1 2 3 4 (4 5 6 4)) 4))