best way to rebuild all perl ports

[jamie at gnix.co.uk]

> Do you have PERL_VERSION= set correctly in /etc/make.conf?

This was set automatically when i first installed perl5.12. This line was later over-written when perl5.10 was installed. Since i used portupgrade to change back to perl5.12 this line has been set correctly. Susbsequent ports i've installed that require perl have been built against 5.12.

	jamie