Hi
petercolapietro,
this Apple guide details upgrading to 5.8.1 as the article states:
"Editor's Note: This article was originally written after the release of Mac OS X 10.2 Jaguar, but the information is still relevant even with the release of Panther. Perl 5.8 is included in the installation of Mac OS X v10.3 Panther, but you may want to install your own version if you plan to customize it; or if you are still running Jaguar."
I am pretty sure you can follow it as a guide for instaling Perl 5.8.8 you downloaded from the Apple site.
Hope this helps.
Martin