Others have pointed out that this is more an algorithm thing rather than a perl thing.
A Google search on "Round Robin Tournament" turned up a couple of interesting links including: http://www.devenezia.com/downloads/round-robin/ with an overview (including graphics) and http://www.devenezia.com/downloads/round-robin/sci.math.num-analysis.round-robin with a discussion on a cyclic algorithm for generating the tables.

--JAS