Perl 6 (rakudo) book (#2299)

* Update free-programming-books.md

* updated Perl 6 list

* Update free-programming-books.md

* Update free-programming-books.md

* Update free-programming-books.md

* Update free-programming-books.md

* Update free-programming-books.md

* Update free-programming-books.md

free-programming-books.md

@@ -132,9 +132,9 @@
 * [OpenMP](#openmp)
 * [OpenResty](#openresty)
 * [OpenSCAD](#openscad)
-* [Parrot / Perl 6](#parrot--perl-6)
 * [PC-BSD](#pc-bsd)
 * [Perl](#perl)
+* [Perl 6 / Rakudo](#perl-6--rakudo)
 * [PHP](#php)
 * [PicoLisp](#picolisp)
 * [PostgreSQL](#postgresql)
@@ -1631,12 +1631,6 @@ For resources on Angular, Backbone, D3, Dojo, Ember, Express, jQuery, Knockout,
 * [OpenSCAD User Manual](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual)
 
 
-### Parrot / Perl 6
-
-* [Perl 6 Programming](https://en.wikibooks.org/wiki/Perl_6_Programming)
-* [Using Perl 6](https://github.com/perl6/book/) (work in progress)
-
-
 ### PC-BSD
 
 * [PC-BSD® Users Handbook](http://web.pcbsd.org/docs/)
@@ -1667,6 +1661,13 @@ For resources on Angular, Backbone, D3, Dojo, Ember, Express, jQuery, Knockout,
 * [Web Client Programming with Perl](http://www.oreilly.com/openbook/webclient/)
 
 
+### Perl 6 / Rakudo
+
+* [Perl 6 Introduction](http://perl6intro.com)
+* [Perl 6 Programming](https://en.wikibooks.org/wiki/Perl_6_Programming)
+* [Using Perl 6](https://github.com/perl6/book/) (work in progress)
+
+
 ### PHP
 
 * CakePHP Framework