If you reverse the order of the arguments you can use pop instead of shift to save two strokes....

Update:

This attempt is about the same length, though a few chars shorter in the actual -e argument. BTW, yours was a very *evil* script... unbalanced brackets in the -e of a -n? I didn't even realize that was legal, let alone useful! ;-)

perl -aF// -ne'INIT{$l=pop}$L=$l.$/;$L=~s/$_// or$#F=0 for@F;$w[@F].="
+@F"}{print$w[-1]'
[download]

-Blake