Hi Michael,
the problematic line in question is
(#t (define *use-gamba-clefs* #t))
If you use set! instead of define it will work. The problem here lies probably
in the switch from guile 1.8 to guile 2. I suppose in that the context of case
changed somehow to not allow definitions.
Keep in mind that define is a bit special in LISP languages. LISP has a strong
functionals base, and that means that we are in a paradigm where e.g. results
should not depend on order of execution.
This requires that a value bound by define is immutable. So LISP languages tend
to be very restrictive of where you can put a define, and usually do not allow
defining a mapping already bound.