If you're going to play 52 Perl Pickup, you might as well use CPAN. :-)

use strict;
use warnings;

use Games::Cards;

my $num_decks = 2;

# Create a deck of cards
my $game = Games::Cards::Game->new( {} ); # default game
my $deck = Games::Cards::Deck->new( $game, 'Deck' );
$deck->shuffle;

# Assemble the pile of cards
my @pile;
push( @pile, map { $_->print() } @{ $deck->cards } ) for 1 .. $num_dec
+ks;
my @sorted_pile = sort @pile;

# Compute the number of decks in the pile (pretend we don't know it)
my $num_decks_calc = scalar @sorted_pile / $deck->size;

# Divide the pile into decks
my @decks;
while( @sorted_pile )
{
    foreach my $decknum ( 0 .. $num_decks_calc-1 )
    {
        push( @{ $decks[$decknum] }, pop( @sorted_pile ) );
    }
}

# Print the results
foreach my $decknum ( 0 .. $num_decks_calc-1 )
{
    print join( ' ', @{ $decks[$decknum] } ), "\n\n";
}
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Note: error checking could be added (missing cards, etc).