This is fun: A REXX XML PARSER.
Check out pup for parsing HTML on the command line. Does pretty printing too.
You can convert an IP address to an int, and vice versa, with these two MySQL functions. Of course I learned about this after I’d already implemented IP address support using BINARY(4) and my own parser/formatter… now that I have my own implementation I can’t bring myself to let it go, and I worry about support for signed/unsigned 32-bit ints (perhaps my concerns are unfounded..?)