[racket] DrRacket and The Little Schemer?

I've been working through The Little Schemer using Petite Chez Scheme and
Emacs, but now I'd like to try DrRacket. I have a large file where I've
been putting all the function defines from the book. Occasionally, I use my
own function names, but mostly I stick with the book's names. My problem is
that when I click Run, errors appear:

add1: this name was defined previously and cannot be re-defined

This happens with all the HTDP language choices. With the Legacy languages
I get:

define-values: cannot change constant variable: equal?

Of course commenting out seems to get me farther, but I'm commenting so
many out! I'd simply like to try DrRacket with TLS and be able to debug and
step through my code. For example, I'd like to find a way to trace through
each step of evens-only*&co
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