https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61425
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> --- Hmm, I guess I shouldn't trust man pages, a POSIX BRE doesn't allow \| Both GNU and BSD grep do allow 'a\|b' in a BRE though ... still trying to determine if it should be allowed for the grep grammar or f this bug's just invalid...
