I see two possibilities here. One, you learn enough about good software engineering and good Perl coding that you can evaluate the code yourself. Or, two, you hire someone you trust to do it for you. I suggest you investigate the second option if you don't have a lot of time for the first. Look for someone well-known in the Perl community who can do a code-review at several points in the project (not just at the end when it's too late to fix anything). Someone with training experience who can help your team learn from their errors would be preferable.

-sam