> Not all syntax-rules implementations are created equal, unfortunately.
Is "tail patterns" incompatibility the culprit again? :-) Or something
about hygiene or phasing.
> I looked into how that library is actually used later on, and it turns
> out it's in only one function in private/chibi-sxml.scm, and that only
> a use of the let-optionals macro that would have worked with the more
> limited version that comes in Chicken's core library. Oh well. It was
> educational, at least.

Right. If that's the only place, my vote is to patch our copy of
chibi-sxml not to require the SRFI.

The downside is that each upstream release of chibi-sxml will have to be
patched, but that library is quite stable and probably won't get many
essential upgrades.