A couple of my friends on IRC have told me this, and since I'm using 10.4.11 I couldn't verify, but the latest Mac OS X Security Update 2009-001 apparently breaks your Perl, if you are using Mac OS X 10.5 (Leopard) and are using Perl that comes with Mac OS X and have upgraded several core modules with CPAN in the past In other words, it doesn't break yours if you a) haven't ever used CPAN with you