Excellent! We need more people from the tech community to mentor and teach the next generation. I was recruited to do a similar class, but I had to teach in VB(agh....stupid school site license). I found that most kids are intrested in two things: 1) They want some sort of finished product that they can use and 2) video games are very exciting to them.
Since your using Perl, you might be able to do a web based project with them. Something like a message board or very simple chat program. Just make sure that when your done teaching them, they have something that they can use and show off.