XSLT
In the course of my new job I’ve been learning a lot more about XSLT (and related XML technologies). This quote really sums up what it’s been like:
… the learning curve for XSLT is quite high, and deciphering it can be a challenge for newcomers. In fact, creating, deciphering, and modifying complex XSLT examples can test the mettle of even the best application developers. To exacerbate this problem, familiar design, development, debugging, profiling, and testing tools used to aid the creation of robust code cannot be used with XSLT. – Source Article
Apparently what I’ve been experiencing is “mettle testing”.