"Perl 6 by Example" introduces Perl 6 using practical, short examples, and explains the language features from those examples along the way.
It features discussions on how to test the code, refactoring to make it more idiomatic, and doesn't shy away from concurrency and keeping persistent state.
The book is currently a work in progress. You can buy a snapshot as an ebook (PDF/epub/mobi) on LeanPub, and receive updates for free as they are published.
A new chapter is typically published every one to three weeks.
Once the manuscript is finished, a print version will likely be made. Plans for the print version are still vague.