After seeing the article on Extending Ruby with C, I thought "I wonder how easy that would be in Perl?" The article is mostly about providing access to the Genx library. So, I spent a little while playing with it and came up XML::Genx. I don't know whether Perl needed another XML writing library; XML::SAX::Writer is pretty good. But Genx has some really useful features.
Anyway, it's been an interesting exercise. My C skills needed bringing out of storage, although I made few really daft mistakes. XS is still an "interesting" tool to work with. Coding at that level certainly makes you appreciate how high level Perl is.
On the whole though, the most useful surprise has been CPAN Testers. That's a really good way to find out that the world isn't just as FreeBSD faced as it looks like to me. Now all I need to do is figure out how to get a development environment working under windows.