Honestly I can't see there's much of an advantage either way. But, since you already have strong perl, and the auction stuff sounds like it may be needing business logic and not just db, you might want to take a look at Catalyst. Demo Catalyst-based handel for your boss, and point out how much has been achieved by strategic code reuse. How many more times this amount of code would you need to achieve the same functionality with PHP? Why, with Catalyst you can build a wiki in 30 lines of code!
in reply to perl vs. php
A lot of that was surely drinking the kool-aid, but after waiting many weeks for the handel demo to come out I'm in a mood to do some flag waving :)