Same as for MCFilter::match.
You want better to use counters and `MCStringGetNativeCharAt()` instead of all the pointer arithmetic, and it will allow you to build properly the substrings - for now, you are always starting from the beginning of the string, but this is not correct: `t_token` stores the starting position of the token in the string, and `t_ptr` the ending point; `t_start` and `t_end` would replace them happily.