This type of shuffle is called a Riffle shuffle. You have enough reading material to satisfy any curiousity about their mathematical properties in the Mathworld entry for Riffle Shuffle and its references (You'll see that it makes a difference if you do an in- or out- shuffle).

japhy has a one-liner to do either-sided Riffle shuffles at Array One-liners. You can make this really succinct if you also use glob to generate the initial deck: 

sub riffle {
    splice @_, @_/2 - $_, 0, pop
        for 0 .. (@_/2)-1;
    return @_;
}

my @deck = glob "{2,3,4,5,6,7,8,9,T,J,K,Q,A}{C,D,H,S}";

for my $shuffle (1 .. 10) {
    @deck = riffle @deck;
    print "shuffle #$shuffle:\n@deck\n";
}

[download]
It might also be interesting to see what happens when you change the riffle sub to: 
## random-sided Riffle shuffle
sub riffle {
    if (rand() < 0.5) {
        splice @_, @_/2 - $_, 0, pop
            for 0 .. (@_/2)-1;
    } else {
        splice @_, @_/2 + $_, 0, shift
            for 0 .. (@_/2)-1;
    }
    return @_;
}

[download]

blokhead

In reply to Re: Perfectly shuffling a deck of cards, over and over by blokhead
in thread Perfectly shuffling a deck of cards, over and over by FoxtrotUniform

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