Just how can you be so confident that no one else has the same problem as you do and yet they might fire up better solutions? What's really new under the sun? And practically, once you release your code, there's nothing you can do to stop people from copying it, assumming it's worthwile after all.
If you need some protection, copyright your Perl modules, put some license, release publicly, and let others peek on them, and they might offer their hands to improve them. In the meanwhile, offer your customer to purchase some services around your modules, and solutions.