This is a case insenstive search and uses the Javascript Regular expression syntax.
Regular Expressions are for advanced users and folks who program. You can start here for more information: JavaScript RegExp Object
Most Autofill users will be well served using the Autofill wizard to create autofill rules for themselves.

TIP: Autofill also supports lookbehind Regular Expression syntax (?<= and ?<!) that is not offered in JavaScript's RegExp object. This allows you to create highly complex text patterns such as the one below, which matches anything that contains "name" but is not immediately preceded by "first" or "last":

   (?<!first|last)name

This will, for example, match "name", "uname", "username", "artistname", and "bookname", but NOT "firstname" or "lastname". Lookbehind syntax only works on the name, id, and class attribute values; you cannot use lookbehinds when matching against field labels.

A brief explanation of the regular expression : .*live\.com/.*(add|edit).*\.com
Match the colors in the expression with the corresponding matches in the target string.

.*live\.com/.* (add|edit).*\.com

http://profile.live.com/P.mvc#!/cid-dc39/details/Add/?break=1&ru=http%3A%2F%2Fco7w.col107.mail.live .com

.             Matches any one character
*             Matches zero or more occurrences of the preceding expression
\             Matches the character following the backslash {Used to Find reserved Reg Exp notation characters}
(|)           Match either a or b {match either string1 or string2}

.*, live, \.,com/

any character zero or more times, live,the reserved Reg Exp char . ,com/

http://profile, live,.,com/

.*, (add|edit)

any character zero or more times, Match either add or edit

P.mvc#!/cid-dc39/details/, Add

.*, \.,com

any character zero or more times, the reserved Reg Exp char . ,com

/?break=1&ru=http%3A%2F%2Fco7w.col107.mail.live, .,com