Benchmark: timing 5 iterations of Algorithm::Permute, Algorithm::Permute qw(permute), List::Permutor, MJD's, perlfaq4...
Algorithm::Permute: 43 wallclock secs (42.93 usr +  0.04 sys = 42.97 CPU)
Algorithm::Permute qw(permute): 15 wallclock secs (14.82 usr +  0.00 sys = 14.82 CPU)
List::Permutor: 227 wallclock secs (226.46 usr +  0.22 sys = 226.68 CPU)
     MJD's: 307 wallclock secs (306.69 usr +  0.43 sys = 307.12 CPU)
  perlfaq4: 272 wallclock secs (271.93 usr +  0.33 sys = 272.26 CPU)