If I understood correctly, a modified list should have been returned.

I should have posted this sooner; sorry.

I have updated the tests. This solution fails now.

Nice catch! I've updated the tests so that that posted solution fails now.

"should evaluate each form only once" probably should change the sign too because this doesn't fail now.

I updated the description. Thanks.

That's the question. And that's a good answer. But it's not trivial.

Don't just tell me, put it in the description.

To be sure I understand the question... What to do when the below happens?

(dosteps (x 5 0 1)
  ;body
)

If that happens, do nothing; don't execute anything in the body, and don't signal an error.

What to do when end comes before start, according to step ?

If you look at line four of the 'for example' section in the description...

"A," = 0B10100000 = ‭160‬ (a + comma)

you'll notice that it is inconsistent. "(a + comma)" should be "(A + comma)". But anyway, fun kata! Thanks.