Well, we're delving into state contract law here, so advice from patent practitioners may be a bit like pears and oranges, if you catch my drift. Where you're located matters. I think Pear is based in California.
Here are a few things that work in your favor. First, you're not hired to develop. Second, I assume you're playing with perl on your own time at your home. Third, I assume that the things you're getting perl to do are completely unrelated to your responsibilities at work. All those things work in your favor, despite whatever draconian clauses you might have in your contract. For example, you don't really have to give them your first-born child, which you obviously created yourself, even if it's in the contract. Same if you make a great souffle'.
If you're experimenting with perl on your work computer(s) and using it to automate some of your work tasks, then the software you're creating probably belongs to Pear.
Lastly, you might consider what you hope to do with your perl creations. Let's say you want to hack a SqueezeBox virtual media player for running on your Wii. Even if Pear would love to own that, it won't come to their attention if you have it running in your home and nowhere else. Even if you release it as open source (and please tell me if you do), it would have to make an awfully big splash to justify mobilizing lawyers to wrestle the code from you. And, even so, the whole thing would go away if you just terminate the project and give them the code.
However, if you think your experiments have value and might seed a great startup idea, then you have bigger problems and ought to seek some legal advice. Once you aim to make big money on your development, there's a greater chance of catching the attention of Pear brass -- perhaps even Steve Knobs. Best to be prepared if that happens.
Welcome to the world of development! Go forth and proliferate!
Regards.