In actual fact, I don't believe Perl deserves 5 stars on all counts (documentation, interface, ease of use); it doesn't even really deserve them in any one count. (To be sure, none of them deserves less than 3 stars either.) But it is a big distribution, with *many* separate things to review. A lot more than three criteria would be required to even attempt a real review, and they'd need a finer scale than 1-5 stars too, and a review wouldn't fit in this margin anyway.
So I give it 5 stars for the great things it has accomplished and continues to accomplish, rather than for what it is, and I think that is perfectly justified.
Perl is one of the few tools I've used constantly since I learned it over 10 years ago. Its uses are many and varied. With each new version, documentation is added or clarified and new features are added that allow perl to be used in an ever-widening array of situations. Perl 5.8.0 is great! I highly recommend it to anyone.