Not a fully formed note/post yet. Just some notes and links.

http://www.cisco.com/en/US/docs/ios/12_0t/12_0t1/feature/guide/cliparse.html#wp5286
http://hackathology.blogspot.com/2007/04/cisco-ios-cli-regular-expressions-part.html

http://hackathology.blogspot.com/2007/02/basic-cisco-ios-router-management-to.html
http://www.handsomeplanet.com/archives/7