I can, but I won't. The OP looked like a homework assignment. My goal was to post a working solution that was as cryptic, compressed, unreadable and definitely un-turn-in-able as possible.

If you are genuinely interested, I would recommend reading:

• perlrun for an explanation of -a -F, and -n.
• perlmod to understand what BEGIN and END blocks do.
• perlfunc for an explanation of the sort function.

Thanks. :)