Microsoft has published a new KB describing the Regular expression support in System Center Operations Manager 2007 and 2012.
In group calculation, PERL regular expression syntax is used and in expression filtering .Net regular expression syntax is used. Tables describing these functions are presented in the KB along with tables for comparison operators and wildcards used for accessing the SDK.
As I have mentioned in an earlier post there is a great way of testing your regular expressions at RegexPal.
The KB article can be found here.