My parser has a grammer which uses '@a' as local variables and '$x' (just like awk) for back-reference in the parse. If I comment this in the parser specification GPPG thinks that the @ and $ is part of the grammar and of course it complaints.
A temporary solution is to quote the $ and @, but as they appear inside a comment it should not be necessary.
/* ('@A' = 77) assign of global local variables */
Refvars ['$1'..'$9'] is accessible references for assignments in
previous run inside a common constraint function block.
The assignment is done in the TOKEN assign rule.