Building and running new package versions not yet in ports?

[Thomas Mueller]

What do I do if I want to build and run a package where version in ports collection is not up-to-date, and I want to build and run the current release version of that package, like Abiword 2.8.6 for instance, when version in ports is behind?  Or maybe I want to try a new alpha or beta development release of a package like Firefox or Seamonkey, but don't want to burn my bridges on the already installed and running version.

Can I create a testing install base such as /extra or /usr/extra, and set something like
PATH=/usr/extra/bin:$PATH
and perhaps modify some other environment variables, and then be able to return to the regular environment?  I would only want to change a few things temporarily and would not want to create an entire chroot system.   

Is this the proper list for this question, or should I have posted to freebsd-ports at freebsd.org ?

Tom