At the time of writing, the current stable major Perl release is Perl 5.22. If you’re using an older version of Perl, you may not be able to run all of the examples in this book unmodified. The examples in this book work best with Perl 5.16.0 or newer, though we recommend at least Perl 5.20. While the term Modern Perl has traditionally referred to any version of Perl from 5.10.1(released on 2009-08-23), the language has improved dramatically over the past several years.