It looks to me like you want something like XPath, and use it on data from the database.

I'd use an ordinary "LIKE" SQL expression to weed out most of the uninteresting results in SQL, and then with XPath, refine it, and extract exactly the data you're after.

As for modules, I may be biased, but I'd look at XML::LibXML's XML::LibXML::XPathContext and XML::LibXML::XPathExpression first.