regex match AND replace

Just to further articulate the regex pattern issue, note that basic 
validation can be achieved with a type MIP and a simpleType definition in 
the model, as shown here:
http://lists.w3.org/Archives/Public/www-forms/2010Sep/0038.html

However, an XPath 2.0 style function matches() would still be useful in a 
constraint MIP and moreover, an XPath 2.0 style function replace() would 
be equally handy.  We are often hitting a situation where we want to match 
a regex and then reorganize the information based on the group matches 
within that regex. 

Cheers,
John