I can't give you actual numbers, but the overall market for Perl books has taken an unexpected turn for the better in the past few months in a significant way. Looking at the graphs, this is largely due to sales of Perl Best Practices, Advanced Perl Programming, Higher Order Perl, and Perl Testing: A Developer's Notebook.
How does this affect you? Well, higher book sales mean more attention for Perl at conferences and in the media, which trickles down to more attention in the tech world in general, which ultimately trickles down to more Perl jobs.
So, to all of you who buy Perl books, thanks for helping me change the world one book at a time.