Regular Expressions with Cisco IOS

I was reaading some cisco stuffs today and i knew long ago that Cisco IOS allows regular expression for simplification of search task and other uses. Well, back then i did not research much on it but i just came across 2 sites which provides more explaination with regards to Cisco IOS regex.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/ftersv_c/ftsappx/tcfaapre.htm

http://www.nil.com/ipcorner/EnhanceIOSUI/