I just have one point to add to the excellent advice given so far. It's actually database related, not anything in your Perl script:

Make sure that the database userid is as unprivileged as possible. I notice you're using mysql and I don't know much about how that compares to other RDBMS but I assume you can have different levels of user, such as sa/dbo/normal, and that you can grant and/or revoke permissions for select/insert/update on individual tables. So make this user as "low" as you can and make sure it doesn't have permission to do anything except insert into the speedtrap table.

Of course, if I'm talking cobblers regarding mysql, then apologies...