5.005 is the 'standard' FreeBSD version, and that fact still annoys me
This isn't strictly true. In FreeBSD-4, 5.005 has been retained as the base Perl to avoid incompatibility problems for users tracking -STABLE. If the version of Perl in the base system changed, these users would also have to update Perl modules when updating the base system. This would likely result in lots of angry users and support problems.
It's easy enough to install 5.6.x from lang/perl5, or 5.8.x from lang/perl5.8 and run use.perl port. The pkg-message file for both these ports, which should be displayed after installation, documents this.
As of FreeBSD-5, Perl no longer ships in the base system to help avoid these problems. In the long term, FreeBSD aims to ship a smaller base system with more functionality moved out to packages.