#!/usr/bin/perl

use strict;
use warnings;

my @random = (qw/a b c d e f/) x 2;
 foreach my $i (reverse 0..$#random) { 
    my $r = int rand ($i+1);
 @random[$i, $r] = @random[$r, $i] unless ($i == $r); 
}
print @random, "\n";