I was thinking prepending and appending aren't rearranging.
The important part of my above sentence was "with something already there".
If $PATH == 'a:b' and you do `export PATH=b:$PATH, then you've basically rearranged it. It may as well be 'b:a'.
You wouldn't do this deliberately, of course, but it happens a lot - people end up with massive PATHs because they blindly prefix when something's gone wrong and it _may_ be the solution.