#!/usr/bin/perl -w
use strict;
$_ = "Ohg vg'f ernyyl n irel fvzcyr gnfx...";
my %caesar;
@caesar{'A'..'Z','a'..'z'} =
    ('N'..'Z','A'..'M', 'n'..'z', 'a'..'m');
my $decoded;
$decoded .= $caesar{$_} ? $caesar{$_} : $_ for split //;
print $decoded, "\n";