Perl 6 is still in the development stages and is probably a long way off yet. When it is released, it will require a completely new rewrite of many of the examples in Perl Cookbook. But since the syntax is still very much in flux, we can't say for sure exactly what it will look like. So anything we'd publish on Perl 6 would not only be useless today, but both useless and out-of-date by the time Perl 6 was a reality.

Perl 6 will require a rewrite of all our Perl books. The changes are sweeping enough that you can't just say "here's how to do it in Perl 5 and here's how to do it in Perl 6" as needed, because it touches practically everything. You can't really expect a book published today to cover both Perl 5 and Perl 6, and do a good job at both.

As an "Essentials" title, it's meant as a sneak-peek at an emerging technology, not as a typical O'Reilly "Definitive Guide." Many people are still very curious about Perl 6, and may need to start developing code today with tomorrow's Perl 6 syntax in mind. Also, the Perl 6 development team is very much in need of money and manpower, and we hope that the Essentials book will help encourage people to contribute to the project. O'Reilly itself is contributing a portion of the profits from the book to The Perl Foundation, and one of the authors of Perl 6 Essentials, Allison Randal, is also contributing a significant portion of her royalties.

However, the book is very clear about the fact that the actual specifics of the language design are still subject to change. Our intention is to update that book frequently until Perl 6 is complete.