regex implementation to replace group with its lowercase version

Question

Is there any implementation of regex that allow to replace group in regex with lowercase version of it?

Answer 1

Several answers have noted the use of \L. However, \E is also worth knowing about if you use \L.

\L converts everything up to the next \U or \E to lowercase. ... \E turns off case conversion.

(Source: https://www.regular-expressions.info/replacecase.html )

So, suppose you wanted to use rename to lowercase part of some file names like this:

artist_-_album_-_Song_Title_to_be_Lowercased_-_MultiCaseHash.m4a
artist_-_album_-_Another_Song_Title_to_be_Lowercased_-_MultiCaseHash.m4a

you could do something like:

rename -v 's/^(.*_-_)(.*)(_-_.*.m4a)/$1\L$2\E$3/g' *