Chez Scheme Transcript [Fri Mar 18 13:59:45 2011]
> (define sum
    (lambda (ls)
      (list-recur ls 0 +)))
> (sum '(3 4 5))
12
> (define product
    (lambda (ls)
      (list-recur ls 1 *)))
> (product '(3 4 5))
60
> (define length
    (lambda (ls)
      (list-recur ls 0 (lambda (x y) (+ 1 y)))))
> (length '(3 5 6 7))
4
> (foo '(a b c d))
(a b c d)
> (goo '(2 3 4 5) (lambda (x) (+ 2 x)))

Error: variable goo is not bound.
Type (debug) to enter the debugger.
> (boo '(2 3 4 5) (lambda (x) (+ 2 x)))
(4 5 6 7)
> (member-item 4 '(3 4 5 6 4 2 4))
3
> (define sum (list-recur-cool + 0))

Error: variable list-recur-cool is not bound.
Type (debug) to enter the debugger.
> (rl)
> (define sum (list-recur-cool + 0))
> (sum '(3 4 5))
12
> sum
#<procedure g>
> (transcript-off)