First explain the reason for the sigils, which is to make it possible to add keywords to the language without breaking old code. I have found that this soothes the initial horror of seeing the language for the first time. I like to tell the story of trying to compile my C code in C++ and what happened to all the variables that happened to be named 'new'.

Then show a few simple regular expressions. Mention that they can become horribly complex, but there is no need to scare them with it.

Next show how to do something useful with a CPAN module by cutting and pasting the synopsis, and then making a few modifications.

If you have sufficient hubris, and are reckless, take a request from the audience and write a program that solves an audience-suggested-problem right in front of them, while explaining what you are doing. Watching a good, experienced coder is incredibly instructive. You could have a shill request a problem in case no one else in the audience has a suitable idea. But you can guess and prepare ahead for a few ideas, such as a log file analyzer and a web scraper.

Another approach to a live coding demo would be to have a Death Match, where two individuals or teams of experienced Perl programmers compete to solve a hard problem in a short amount of time. Switch the projector back and forth between the two teams, and add color commentary. I learned the cut-and-paste-the-synopsis trick from watching a Death Match, and I have used it dozens of times since then. That challenge was to write a mail reader in 20 minutes!

One more thing - be sure to show off ptkdb. I realize that lots of people here don't like debuggers, but they are expected and ptkdb is very nice.