Chez Scheme Transcript [Thu Mar 10 14:43:34 2011]
> (load "foo.ss")
> (facT 5 1
    )
120
> (trace facT)
(fact)
> (facT 5 1)
  
    )
|(fact 5 1)
|(fact 4 5)
|(fact 3 20)
|(fact 2 60)
|(fact 1 120)
|(fact 0 120)
|120
120
> (define m 3)
> m
3
> (lambda (n) n)
#<procedure>
> +
#<procedure +>
> *
#<procedure *>
> (+ 3)
3
> ((lambda (n) n) 3)
3
> ((lambda (n) (+ n 1)) 3)
4
> ((lambda (n m) (+ n m)) 2 3)
5
> (define foo (lambda (n) n))
> foo
#<procedure foo>
> (foo 42)
42
> (define foo +)
> (foo 3 4)
7
> (define + *)
> (+ 3 4)
12
> (define + /)
> (+ 8 2)
4
> (define #t #f)

Error: invalid syntax (define #t #f).
Type (debug) to enter the debugger.
> (exit)