Upgrading Perl on a Solaris 9 box

I'm working up updating SpeedyDog's bugzilla installation from 2.16 to 2.20. I'd been getting nowhere trying to use CPAN to update the perl packages necessary - I kept getting a "Error in server response, closing control connection." message.

Turns out you need to run
export FTP_PASSIVE=1
before firing up CPAN.

Simple, and easy to find via google, but good to know. I wish that the CPAN error messages were a bit more useful.