Custom-built Text Processing

The dark side

The Desperate Perl Hacker This legendary character haunted early discussions of XML, acting as a force for keeping XML easily processed without proper XML parsing support.
Regular expressions are powerful They're almost as inscrutable as XSLT, but regular expressions provide developers with some incredibly powerful text manipulation tools. (Warning: regexes also need documentation if you hope to maintain them.)
Not 'the XML way' Bring up text processing of XML documents on XML-dev, and you're likely to get a few flaming arrows aimed in your direction. Sometimes, though, the XML way isn't the only way, even with XML documents.