ISSETBACK          42 ereg/regex/regexec.c #define	ISSETBACK(v, n)	((v) & ((unsigned)here >> (n)))
ISSETBACK          66 ereg/regex/regexec.c #undef	ISSETBACK
ISSETBACK          91 ereg/regex/regexec.c #define	ISSETBACK(v, n)	((v)[here - (n)])