re_string_peek_byte
c = re_string_peek_byte (input, 0);
char prev = re_string_peek_byte (input, -1);
c = re_string_peek_byte (input, 0);
c2 = re_string_peek_byte (input, 0);
c2 = re_string_peek_byte (input, 1);
if (ch == delim && re_string_peek_byte (regexp, 0) == ']')
return re_string_peek_byte (pstr, idx);
return re_string_peek_byte (pstr, idx);
return re_string_peek_byte (pstr, idx);