sub shuffle
{
    my @in = @_;
    my @out;
    push @out, splice(@in, rand @in, 1) while @in;
    @out;
}

##</code><code>##

use strict;

use Benchmark qw(cmpthese);

my @cards = 1..52;

cmpthese(-1,
         {
             shuffle => sub { shuffle(@cards) },
             random_perm => sub { random_perm(@cards) },
         });

sub random_perm {
  my $n = my @p = @_;
  for ( my $i = $#p; $i > 0; --$i ) {
    my $j = int rand( $i + 1 );
    @p[ $i, $j ] = @p[ $j, $i ];
  }
  return @p;
}
sub shuffle
{
    my @in = @_;
    my @out;
    push @out, splice(@in, rand @in, 1) while @in;
    @out;
}

##</code><code>##

              Rate random_perm     shuffle
random_perm 6000/s          --        -30%
shuffle     8606/s         43%          --