A good place to read about sorting in Perl and specifically the "Schwartzian Transform", is Shlomo Yona's lecture slides on Sorting in Perl:
http://yeda.cs.technion.ac.il/~yona/perl/lecture5/index.html
This will give you not only a good explanation of the Schwartzian Transform itself but will also put it in context with other sorting techniques. Check out the "Orcish Maneuver" - sounds like something you would do in World of Warcraft :-)