sub add_item {
    my ($dbh, $cart_ref, $item_id, $qty, $color) = @_;
               
    # If the item isn't already in the cart, look it up from the database
    # and store it in the cart as a new entry with a quantity of zero.
    my $saw_item = 0;
    foreach  my $item (@{$cart_ref}) {
        if (($item->{'id'} == $item_id) && $item->{'color'} eq $color)) {
            $saw_item = 1;
            break;
        }
    }
 
    if (!$saw_item) {
        my $sth = $dbh->prepare ("SELECT item_id, description, category, price, picture, thumbnail, mime_type, color FROM catalog_pet WHERE item_id = ?");
        $sth->execute ($item_id);
        my $row = $sth->fetchrow_hashref ();
                                 
        return if !defined ($row);    # this shouldn't happen...
        my $item_ref = {};
        $item_ref->{description} = $row->{description};
        $item_ref->{price}       = $row->{price};
        $item_ref->{qty}         = 1;
        $item_ref->{color} = $color;
    }
    $item_ref->{qty} = $qty;
  
    push (@{$cart_ref}, @item_ref);
}