I think he's asking how he can detect the "whole filename changed", although he almost provided the answer: use a pattern describing what you're expecting to see and match the filename against that. If the filename doens't match, it changed beyond your expectations ("the whole filename changed").

Two nits: you don't need the capturing (to do this, at least) and you'd want to anchor the pattern to the beginning and end of the filename.

— Arien