>From a recent bug report (by Stavros):
I tried setting Berlefact:false to see if that would make a
difference, but that causes an internal error (POWERSET requires
less than two arguments).
This is because set.lisp redefines POWERSET (originally defined in
ratout.lisp). Please suggest a different name (only for POWERSET, not
for the user-visible $POWERSET).
Wolfgang