All,
This is my first attempt at intentionally writing obfu though I once accidently created some. Now it won't be hard to unravel since I have already explained how it works.

#!/usr/bin/perl
use strict;
use warnings;

my $label;

($_) = <DATA>;
my $magic = join '', map {chr hex} /(..)/g;
eval $magic;

$label = 'START';
print "$label\n";

goto $label;
print "This will not print\n";

START:
print "Hello, world\n";
exit;

END:
print "Goodbye, cruel world\n";
__DATA__
7b6e6f207761726e696e67733b6e6f207374726963743b2a5449455343414c41523d73
+75627b626c6573737b7d7d3b2a53544f52453d7375627b7d3b2a46455443483d73756
+27b24612b2b3f454e443a53544152547d3b746965246c6162656c2c6d61696e7da
[download]

I welcome contributions that better obscure the "setup". It would have been even better if goto worked inside a tied call. Be sure to use the download link as linebreaks in the DATA segment will currently cause it not to function correctly.