Does Calibre use a special "flavor"of regex?

I am by no means an expert with regex's, but I find that a lot of the things I have used in the past (in programming, not Calibre), do not work.

I have looked at the Quick Reference on the calibre site, and there are things I don't recognize. This could be simple ignorance on my part of course.

Is the calibre regex a different variety? If so, is there a more comprehensive reference out there that would inform me.