Programming Perl, best known as the Camel Book among programmers, is a book about writing programs using the Perl programming language, revised as several editions (1991-2012) to reflect major language changes since Perl version 4. Editions have been co-written by the creator of Perl, Larry Wall, along with Randal L. Schwartz, then Tom Christiansen and then Jon Orwant. Published by O'Reilly Media, the book is considered the canonical reference work for Perl programmers.