I would rather have a wise and experienced developer X than a developer with Y experience in Z.

As long as you are hiring people with skills in solving similar problems to the ones you are having or are anticipating on having.

Edit: However that may not work for you. I think that a senior Perl developer would be more than competent in any language you point towards. While the opposite may hardly hold true. The presumption is that one believes that a senior Perl developer really exists.