Chez Scheme Transcript [Fri Mar 11 11:54:32 2011]
> (let ([foo (lambda (n) n)])
      (foo 4))
4
> ((lambda (foo) (foo 4)) (lambda (n) n))
4
> (let ([fac (lambda (n) (if (= n 0) 1 (* n (fac (- n 1)))))]) (fac 5))

Error: variable fac is not bound.
Type (debug) to enter the debugger.
> ((lambda (fac) (fac 5)) (lambda (n) (if (= n 0) 1 (* n (fac (- n 1))))))

Error: variable fac is not bound.
Type (debug) to enter the debugger.
> (transcript-off)