You asked, and we (eventually) delivered.
Modern Perl, the book, is now available in ePub format as well as A4- and letter-sized PDFs.
There is no DRM and there are no special licensing terms. Please redistribute this book far and wide and tell everyone that they too can write great Perl 5 code that takes advantage of all of the hard-earned wisdom and effort we've put into improving the language in the past several years.
Of course, you can always tell people to buy the printed copy—I'm a fan of paper—but the important part is spreading the word, whether through reviews on Perl Monger lists, web sites like Slashdot and Ars Technica and LWN, and of course booksellers. You're also very welcome to upload and seed torrents, post it on ebook sites, or just hand around USB sticks whenever you get together.
Bilingual Perl hackers have already begun translations into other languages, and we're very happy to see this and help in any way possible.
If we're going to show off how great Perl programming can be, let's make sure everyone has a chance to read a good book about it.