The abstract says the SRFI supports "every major implementation
currently in use" but Gerbil is missing from the listings. It has its
own keyword syntax which seems modeled after Gambit's. Gerbil also has a
distinct macro system which is why I postponed implementation. I'll get
to it in a while; but if someone else wants to do it, I'll happily
accept their contribution. The macros are not very complex and there are
plenty of examples of other Schemes (including Gambit) at
<https://github.com/scheme-requests-for-implementation/srfi-177/tree/master/srfi>.