Below is a sub I've written to figure out all the possible arrangements of the elements of an array. Is there a cleaner and/or more efficient way to do this? I'm assuming that it would be possible to do this by swapping elements, thereby not copying the array each time, but I can't determine the order you'd need to swap them in. 

sub combinations {
  my @array = @_;
  if ($#array == 0) {return [ $array[0] ]; }
  my @results;
  my $element;
  foreach $element (0..$#array) {
    my @leftovers = @array;
    my $chosen_one = splice(@leftovers, $element, 1);
    foreach (&combinations(@leftovers)) {
      push(@results, [ $chosen_one, @{$_} ]);
    }
  }
  return @results;
}

use Data::Dumper;
print Dumper(&combinations(qw(a b c d)));

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In reply to Permutations by octothorpe

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