Hi,
Most Perl developers with a web development background will have database experience. I guess you must also look for a person who has strong OO skills. This way, you'll be sure that he will not couple the database too tightly to the application code.
Trust me, there is a big difference between Perl developers out there. All have there own set of skills that are usefull for their job. But what you want is a generalist Perl application developer that has sufficient backing in database design, OO design and Perl coding.
What I would do is to use the following keywords in the job advert; Strong knowledge of Perl, Database design and OO architecture.
I even would go so far as to ask for prior art in applying the MVC design pattern ... as this is a classic design pattern that forces - if applied correctly - to break up the application logic and the coupling to the database and UI...
Just me 2 cents ...
Johan