I sat down the other day to re-look through David Thompson guile-bstructs library, as a learning exercise.
I re-learnt a few things I didn't know before. Like how far it's possible to push syntax-rules/case. I've never quite seen anything like it before.
I've said it before, but scheme syntax-rule related stuff isn't the most intuitive thing. Fear of Macros is still the best explanation I've read; but doesn't show off the capability quite like that library does.