The latest version of Perl 5 is almost entirely backwards compatible with every earlier versions of Perl 5. ( There are some features which almost no-one used,

The latest version of Perl 5 is almost entirely backwards compatible with every earlier versions of Perl 5. ( There are some features which almost no-one used, that also should never be used that were eventually removed ) Perl 5 is backwards compatible with Perl 4 Perl 4 is just a renamed version of Perl 3 to coincide with the release of the book "Learning Perl" Perl 3 is backwards compatible with Perl 2 Perl 2 is backwards compatible with the original Perl Many of the problems that new Perl programmers have with learning Perl is that every new feature had to be added in a way that it didn't break existing code. That is why for example you have to add "use strict" and "use warnings" to every Perl source file, even though that should be the default. Perl 6 exists because we "wanted to break everything that needs breaking", so it is very different than any previous version. That is why both Perl 5 and Perl 6 will both continue to be supported languages. Imagine taking good ideas from every high level modern programming language, bringing them all together, while making the features seem like they have always belonged together. That is Perl 6. I like to say that as Perl 4 is to Perl 5 is to Perl 6, C is to C++ is to Haskell,C#,smalltalk,BNF,go, etc