If you're teaching to beginners, I'd strongly suggest picking up a copy of merlyn's Learning Perl. That book is based on experience teaching Perl to beginners, and you may get some good presentation ideas.

I'd also strongly recommend not just saying, "Here's a variable, here are our datatypes", but rather lifting what Programming Perl has to say about the linguistic analogs of variable names. In particular hash lookups should be pronounced "of". So for instance $age{'Peter'} should be read "the age of Peter". Not only does this help cement what hashes are for, it also tells you what to name them!

Another recommend. Somewhere along the line give them an overview of the steps between a CGI program and the browser. And be sure to start them off with programs that do not involve a webserver, just to simplify things. Remember, people's brains are not built to pile facts on facts in a big tower. We all have limits which, when we run into them, we just balk and stop working. Try not to hit those limits too quickly, and try to recognize it when you have. One piece at a time.