Programmers who don't see the importance of untainting data
Programmers who immediately hit up Perlmonks or clpm asking a basic question when perldoc whatever would suffice
Clients who harp on deadlines, yet do not return calls or get information back to the programmers in time for them to meet the deadlines.
People who say, "You program in Perl? I've tried to pick that up, but it looks like gibberish."
People who don't appreciate good gibberish when they see it. :)
Ex-programmer bosses who say, "Hey, I could have had this fully-working CGI application working in three days, why is it taking you a week?" I mean, who cares if his programming came in the form of 24-hour code marathons and mine was limited to 8-10 hour days.
People who seriously get heated about their choice of text editor. I mean, come on! We all know vi is the way to go, so stop your whining.
Perl code that uses C-style for loops instead of foreach, etc.
People who can't smile at the subtle beauty in calling a reference to a array containing references to hashes. Perl's native data structures are a beautiful thing.