I am, for the most part, self-taught in Perl. I have taken two instructor led courses, though. One was through a community college and was an on-line course in Perl and CGI. The lessons were posted on the web with instructions, tasks and quizzes. Students could work through them somewhat at a self-paced rate. There was some commentary and web-based discussion available. In spite of the structure, it felt more like I was teaching myself, with the added benefit of having someone to consult if I needed to ask a question. The other course was a day long seminar. While the instructor was interesting and knowledgeable, there was just too much covered too quickly to be of any use. I ended up taking the materials home and teaching myself.

For myself, one benefit of instructor led training is that it gets me going in some direction and gives me a goal. I learn best when I am doing something. If I don't have a task or goal in mind then I find it more difficult to actually sit down and work on coding. Lately, I have quite a few interesting problems to solve with Perl, so I'm teaching myself new stuff every day and I don't find an instructor to be necessary.

You mention that you've had a programming language course. I have taken some college courses in Program Design and Logic, and other CIS related stuff. These have proven invaluable as an aid to understand Perl programming specifically.

And the number one reason for an instructor led course (YMMV)--you get a transcript or a certificate, or some other hard-copy bit of documentation to wave at your employer and prove you are "qualified"(at least enough to appease HR).