'subst' argument is described like this:
> subst can be a string, an integer or symbol indicating the contents of a numbered or named submatch of re, 'pre for the substring to the left of the match, or 'post for the substring to the right of the match.
what's missing is, 'subst' can also be a list of these symbols,
numbers or strings. I thought regexp-replace was very limited (if it
only supported either int, sym or str), but this makes it much better.
Chibi test suite does test this case.
I believe this was an oversight. Irregex, (chibi regexp), and SCSH all support lists for subst.
However, as it's not broken but just less useful I don't think it's suitable for an errata.
I agree it's fine for the srfi itself. In the context of r7rs-large though, I think if we already see some shortcomings then we should try to address them before it's finalized. If you agree but are busy, I could try making a new srfi, slightly modified from this one, to cover this. Assuming that John will be ok with voting the new srfi too.