RE_NO_BK_REFS     152 lib/regex.h    # define RE_NO_BK_REFS (RE_NO_BK_PARENS << 1)
RE_NO_BK_REFS     122 test/manual/etags/c-src/emacs/src/regex.h #define RE_NO_BK_REFS (RE_NO_BK_PARENS << 1)