This will also be covered in coming paper but for now have …

This will also be covered in coming paper but for now have a look at xhliu's "tokens without backtracking (almost)" and then @702's comment in this thread: https://powping.com/posts/a8323f5a627b1e26ba6d5493b6c61fdb238c0c439017ee265e4fc307d021cfb6