Good work, you had me stumbling over it for quite a while there, took quite a bit to get the basic algorithm down. That said, I think you did a good job encoding your data. Your next step would be to hide it around the place so that it doesnt all originate from @_

I had a bit of a fiddle, so here's what I came up with using the same data.

$==-1;$=++,$;[abs $_]=/.*\.(.*)/?$1:$=for @_;print map chr $_+65,@;

It gets one char wrong, but I figured it wasnt quite worth the effort to fix that up :)

- nashdj