Partly off-topic, but the Perl documentation used to be really, really good - around Perl 4.x or early 5.x or so. (Not saying it is worse now, just have't looked at it after that.) There used to be (either one or many) PDF files, that had info on pretty much any aspect of the language. The PDFs also looked very good. Excellent font. Not a typography expert, just going by the impression it made on me.