What, no curses? What about a pager or man? Interesting, similar efforts have been made including the now defunct perlix.

If you manage to implement or concede an installation of X there's always PerlBox. It should be possible to implement a wide variety of mail systems using Mail::Box. Finally, I'd like to point out a cron; in perl and whichpm.

UPDATE: Other bits of interests are Dominus' units, and someone's calculator elca