Vinegere

#!usr/bin/env perl
use common::sense;
use autobox::Core;

my @word = map { ord $_ } split '', uc $ARGV[0];
my @key = map { ord $_ } split '', uc $ARGV[1];
for (my $a = 0; $a <= $#key; $a++){
    ((($word[$a] + $key[$a])%26)+65)->chr->print if ($ARGV[2] eq 'e');
    ((($word[$a] - $key[$a])%26)+65)->chr->print if ($ARGV[2] eq 'd');}

#Aureliano Guedes
#Forum Invaders