If you are already checking things, you may be able to turn on Taint mode and not see a difference. Basically, to untaint something, you need to run it through a regex. If that is how you are data checking you're fine.

Do you need to turn it on? No, especially if you are never using the user input to do anything programatically. But it is a nice reminder.

If you're interested in making your form checking a little easier, check out Data::FormValidator. It helps with data checking and untaints your data as a side benefit.