Ponies are the truth
Did you know you can modify perl's readonly constants for undef, true and false? Yep.
&Internals::SvREADONLY( \ !!1, 0 );
${ \ !!1 } = 'ponies!';
&Internals::SvREADONLY( \ !!1, 1 );
print !!1; # ponies!
Same thing for \ undef and \ !!0.
That's the most evil code I've seen in a while. Potentially useful, but definitely evil.