Why would you write this at all? There are a number of pre-existing solutions to searching for information inside PDFs; Google's Search Appliances, for example. Most of these solutions allow you to search quickly inside many types of document. It's got to be cheaper to buy an appliance than to spend your time building a search engine... especially since you're new to Perl.
Searching is harder than it looks: let someone with way more resources than you solve the problem, and just use their solution!
Ramblings and references
“A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort.” — Herm Albright
I haven't found a problem yet that can't be solved by a well-placed trebuchet