Preforming an upgrade should remove the older version of a port

[vendion@…]

When preforming a upgrade on outdated ports it should remove the older version of a port when upgrading to a newer one. This will cut down on unnecessary disk space usage. Taking Perl for an example there is no reason why Perl 5.8, Perl 5.10, and Perl 5.12 is installed at the same time. This is just one of many ports on my system like this.

[blb@…]

That's actually by design; that way, if something breaks when upgraded you can simply reactivate the older, working version. If you truly want to uninstall the older version, use the -u switch:

$ sudo port -u upgrade outdated

From man port:

-u uninstall non-active ports when upgrading and uninstalling