use strict;
use warnings;

use Algorithm::Loops 'NestedLoops';

sub derange {
  # Generate the list of possible values at each position
  # Skip a value if it's already used up (no more in the pool) or is in its original position
  my %pool;
  ++$pool{$_} for (@_);
  my @orig = @_;
  no warnings 'numeric';
  my @values = sort {$a <=> $b or $a cmp $b} keys %pool;
  my @prev_values;
  NestedLoops(
    [(sub {
        # Generate all candidate values for this position
# print "Generating with \@_ = @_\n";
        my $pos = @_;
        # Update the pool: the last value on @_ has just changed, so
        # return the previous value(s) to the pool and remove the new
        # one.
        if (@_) {
          for (grep {defined $prev_values[$_]} $#_..$#orig-1) {
#print "Returning $prev_values[$_] to the pool\n";
            ++$pool{$prev_values[$_]};
            undef $prev_values[$_];
          }
#print "Removing $_[-1] from the pool\n";
          --$pool{$_[-1]};
#print "Valid values in the pool:\n";
#while (my ($k,$v) = each %pool) {
#  print "$k: $v\n" if $v;
#}
          $prev_values[$#_] = $_[-1]; 
        }
        [ grep {$orig[$pos] ne $_ and $pool{$_} > 0} @values ]
      }) x @orig]
  );
}

my @results;
my $iter = derange(@ARGV);
print "@results\n" while @results = $iter->();