Hai brian,
This seems nice suggestion, everyone searches the answer for to solve their own work to complete in faster manner. In my experience i saw some my friends refered the books in following ways,

Looking for proper explanation like syntax and its use in real time. Where they fit for their wok to complete. Basically they are looking differnce questions. somewhat likes My, Local , our differnce questions.

This explanations would give some good idea to Where the "My" fit and where "our" is fit. Example of problems occurs in practical real time and the solution for that problem answers.

categorise the Problems like file related, Regexp, and directory related...

And i would like to suggest To prepare the common FAQ like book or site. that is the collection of Most user asking questions in Perl monks site.

Everyday the new user asking question somewhat older ones and searching for their answers. if this Book or Site created, Most of the user Would get clear idea and They wont ask these kind of questions.

And one thing if anyone wants to refer the new book the cost of the book is high. so they finaly leaves their buying idea and they start trying for alternatives. So all the books should available in less cost or free of reference.

Thanks,
perlsen