Regular expressions are a broad issue, start out a google search for PCRE (Perl-compatible regular expressions), that's the library mIRC uses.
Here's the
wiki entry , the
"pcre homepage" is down atm.
This page might be a point of reference, too.
In addition, there is a really helpful "introduction to regular expressions" and a "extract from pcre manual" for mIRC in the "mIRC Script Box" available at
Merlin's page (online and .chm file) - unfortunately this page is down as well. Maybe one of your friends did download this comprehensive file and can share it with you.
I also like
this tool.
