pattern matching possible?

I have an XML document that has this structure:

  <applications>
       <application>
            <app_name>ABC</app_name>
      </application>
       <application>
            <app_name>DEF</app_name>
      </application>
  </applications>

I'm wondering if there's a way using XPath and some pattern to find
case *insensitive* matches for a particular app_name??

For example, if I have app_name 'ABC' and I want to determine if there
are any existing nodes that have app_names like 'ABC', or 'Abc', or
'abc', or 'aBC', etc.  Is there some version of  'selectSingleNode' with
a pattern that can do that?  AFAICT there aren't any case
(in)sensitivity functions in XSL or XPath.

TIA.

Hardy Merrill