regEx is a powerful instrument to find text.
Maybe too complicated ? Or just a question o taste.
For regEx friends gf supports this.
Internets Wiki https://en.wikipedia.org/wiki/Regular_expression
Unfortunately we have different dialects of the same idea - this does not make it easy to start.

Internals: regEx Implementation of gf is based on Qt.
Qt team say it's Perl-like regular expressions and their pattern syntax
https://doc.qt.io/qt-5/qregularexpression.html

Example of regEx to find all email adresses in all text files

([\w\.]+@[\w\.]*)

Try out - copy expression into clipboard, paste into search field and do not forget to check regEx - otherwise regEx will be interpreted within wrong search methods

Example of regex to find all html <title>

<title[^>]*>([^<]+)</title>