watch for the `%options xregexp` setting when we go and set things up for regex set minification: when that option is NOT set, we must not recognize \pNAME regex sets as matching/contained-in our current regex sets.
watch for the `%options xregexp` setting when we go and set things up for regex set minification: when that option is NOT set, we must not recognize \pNAME regex sets as matching/contained-in our current regex sets.

GerHobbelt/jison-lex,GerHobbelt/jison-lex