Have not tried this, but I have run into this same thing. Took a look at List::MoreUtils and noticed the natatime EXPR, LIST which seems like it might do exactly what you want assuming you read your __DATA__ into an array. You did not specify whether or not the use of modules was ok for you, so I just assumed it was.

From the docs:

Example:

    my @x = ('a' .. 'g');
    my $it = natatime 3, @x;
    while (my @vals = $it->())
    {
        print "@vals\n";
    }
This prints

    a b c
    d e f
    g
[download]

Does that suit your requirements?