There was a good blog article posted a while back regarding the virtues of Perl. It's mostly positive, but there are some valid gripes in a few of the users' comments following the article. Here's a link:

Perl is Dead (Long Live Perl)

There's also a lot of good material in Larry Wall's presentation a the Atlanta Linux Showcase:
Camel Lot #6

This talk was given in October 2000, so it may seem a bit dated with respect to perl6, but all the background/history of perl is still relevant. I especially like the stuff about "manipulexity" and "whipituptitude".