[Boost-users] [regex] - bk_parens and bk_braces missing from 1.33.x

It states in history.html for regex 1.33.0 that "some of the more esoteric options have now been removed, so there is the possibility that existing code may fail to compile: however equivalent functionality should still be available". I suppose bk_parens and bk_braces could be considered esoteric, but I cannot find any equivalent functionality. Is that intentional? Thanks, Keith MacDonald