I've never seen `split_off_mut` but I do use `split_at_mut` quite often to solve similar issues. Using a slice instead of using a Vec directly also tends to gre

I've never seen `split_off_mut` but I do use `split_at_mut` quite often to solve similar issues. Using a slice instead of using a Vec directly also tends to greatly simplify things. I also don't fully understand the buffer reuse example. Why would you want to store references to a string after the string ceases to exist?