ONIGENC_STEP_BACK 3008 regexec.c            s = (UChar* )ONIGENC_STEP_BACK(encode, str, s, end, (int )tlen);
ONIGENC_STEP_BACK 3017 regexec.c            q = (UChar* )ONIGENC_STEP_BACK(encode, str, s, end, (int )tlen);
ONIGENC_STEP_BACK 4219 regexec.c            UChar* pre_end = ONIGENC_STEP_BACK(reg->enc, str, end, end, 1);
ONIGENC_STEP_BACK 4226 regexec.c      	pre_end = ONIGENC_STEP_BACK(reg->enc, str, pre_end, end, 1);