The most recent production release is 5.6 (although 5.005_03 is still supported). The most cutting-edge development release is 5.7.
(from http://www.perldoc.com/perl5.8.0/pod/perlfaq1.html) These version numbers are a little outdated. Kurt H. Maier, CIV Publications Technician IDR / TDSC 270-956-2891
