Benchmark: timing 5 iterations of Abigail's, Algorithm::Permute, Algorithm::Permute qw(permute), List::Permutor, MJD's, perlfaq4...
Abigail's: 9 wallclock secs ( 8.07 usr + 0.30 sys = 8.37 CPU)
Algorithm::Permute: 5 wallclock secs ( 5.72 usr + 0.00 sys = 5.72 CPU)
Algorithm::Permute qw(permute): 2 wallclock secs ( 1.65 usr + 0.00 sys = 1.65 CPU)
List::Permutor: 27 wallclock secs (26.73 usr + 0.01 sys = 26.74 CPU)
MJD's: 32 wallclock secs (32.55 usr + 0.02 sys = 32.57 CPU)
perlfaq4: 36 wallclock secs (35.27 usr + 0.02 sys = 35.29 CPU)