IMO I think its reasonable to expect an experienced developer to have both good perl and good DB skills. There are lots to get wrong in both arena's (poor db layout, index strategy and normalisation, or, coupling of HTML with perl, unlayered approach and poor application design), and depending on the scale/scope of your project these may be critical areas you cannot afford to skimp on in your archeticture design.

I think it would be unreasonable to ask a grad to come out and design an application that will scale in performance, extensibility and maintainability, however these are the cheapest carbon units on the market.

The interview process is important to weed out the "potentials" from the "havent got a chance"'s, but bottom dollar, you get what you pay for.