Finding all the Perl books

I'm looking for a way to discover all the books ever published about
Perl. Where should I look?

* Is there a Perl interface for the WorldCat APIs? If not, I'll make
one. Are people merely shoving their results into something like
XML::Feed? I have a big dump of data

* WorldCat has many of the books, but there are holes. I realize that
this is a union catalog instead of a historical database.

* I know about the Amazon interfaces too, but I think that's the same
problem as WorldCat (and there are already Perl interfaces for that).

* I have the data dump from Google Books already.

* I figure that the Library of Congress knows about a lot of them, but
I don't have $20,000 to buy their 2012 database (or subsequent ones).
Is there some other way to get re

-- 
brian d foy <[email protected]>