<p>I'd like to use regular expressions in selecting elements using the match function.  I'd prefer not to use an external library (such as saxon) to do this.  </p>

Yes, 3.5 XPathNavigator supports XSLT 2.0.
http://msdn.microsoft.com/en-us/library/system.xml.xpath.xpathnavigator.aspx
"The XPathNavigator class in the System.Xml.XPath namespace is an abstract class which defines a cursor model for navigating and editing XML information items as instances of the XQuery 1.0 and XPath 2.0 Data Model."