I'm not sure it's of the same caliber and complexity as a TCP/IP stack, but I have recently started poking around an old project of mine
as some people I work with have expressed interest in a completed working version, and I've been looking at a Perl implementation.
I really wish I knew more about Perl/C compatibility back in the day when I was initially working on this, it would have made parsing the cue sheet files a lot easier, but apart from that I've been looking into some different methods for using Perl to play the audio itself in a cross platform way. Drawing a GUI for the Windows folks might also come in handy.
I know it's probably nothing especially hard, it's just more time consuming than I have time for at this moment. Story of my life, really :)