use strict;
use warnings;

sub derange {
  my @list = @_;
  # Swap every element with something higher
  my $start = int rand @list;
  for (0..($#list-1)) {
    my $this = ($start + $_) % @_;
    next if $list[$this] ne $_[$this] and $_ < $#list-1 and rand > .52;
    my $other = $_ + 1 + int rand($#list - $_);
    $other = ($start + $other) % @_;
    @list[$this,$other] = @list[$other,$this];
  }
  "@list";
}

my @ar = ('a'..'d');
print "@ar\n";
my %countem;
$countem{derange @ar}++ for 1..5000;
print "$_: $countem{$_}\n" for (sort keys %countem);