PS Even without the multiple cleanup-form extension, I shouldn't have
coded (lambda () <expr>) in the macro text. One should always code
this like (lambda () (values) <expr>) or even better (lambda ()
(values <expr>)) so that an error is likely to be reported when a
non-expression is provided for <expr>.

Am So., 9. Okt. 2022 um 17:13 Uhr schrieb Marc Nieper-Wißkirchen
<xxxxxx@gmail.com>:
>
> Am So., 9. Okt. 2022 um 17:03 Uhr schrieb John Cowan <xxxxxx@ccil.org>:
>
> >> Thanks; with my definition, I would have to code it like
> >> (unwind-protect protected-form (begin (values) cleanup-form ...)) as
> >> otherwise definitions would be allowed by the definition making it too
> >> easy to write non-portable code.
> >
> >
> > Eh?  `Begin` doesn't allow declarations; only `lambda` and the `let` family do.
>
> My proposed macro has
>
> (lambda ()
>   <cleanup-form>)
>
> as a subform.  Expanding a begin in this context would have the
> meaning of the first form of begin in section 4.2.3 of R7RS ([1]).
>
> --
>
> [1] In fact, the first form of begin should probably not have been
> listed in this section at all but somewhere else because it is not an
> expression form.