[racket] Printing and doing something does neither - why?

Hi,
I am wanting to both print something and do something.
I found an example in the Racket guide p.20 sec.2.2.1
Only nothing comes back in the interactions.
It runs fine - no errors, but appears to do nothing.

Both printf and string-append are suppose to be in racket and racket/base.
Any ideas?
Thanks, Carolyn

The code: (using Racket ver.5.1.1)
#lang racket
(require racket/base)

(define (bake flavor)
(printf "pre-heating oven...\n")
(string-append flavor " pie"))
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