It looks a little bit. Search for Search "chor[a-zżźćńółęąś]*\s?ryb" browsing "choroba", "chorobowych"

Sorry, but didn't work for me. After searching, there were never any matches. Turned off regex, tried, but nothing.

Why on Earth this add-on need "Access your data for all websites"? BEWARE. Regex Search does not ask so intrusive information.

It slows the browser A LOT when trying to find anything on a large web page (the most popular use case). It is probably because of "search as you type" functionality. It should be possible to deactivate it. The other possibility is to perform "search as you type" only for expressions longer than e.g. 3 characters. I dislike also a very broad permissions this addon requires. It can be a security concern. Addon named "Multiple Highlight" shows that it is possible to search RegEx without any permission requested.

I don't know if it is a coincidence or not, but ever since I installed this extension I've been constantly getting redirected to under2given(dot)com. It hasn't stopped so I had to uninstall. But it still continues! I don't know what sort of malvertisements your team is offering, but I truly do not appreciate this constant harassment .
(If you need more details as to what I have been doing is I was on Reddit and used this search function (didn't help me, by the way) and then I went to YouTube. That was it. So it certainly was not the websites that I have been on.)

Was looking for a way to use regex searching in FF. Does not seem to work at all. Opened a source code view and tried my regex. Nothing. Tried a simple search for href (there were plenty on the page!) Nothing. Not working at all, uninstall.

It does not work... :-(