Since Rakudo is a compiler, you have to distinguish between documentation for the compiler itself, and the language it implements. The main documentation for the compiler itself is its manual page..
Documentation for Perl 6 can be found in different places:
- doc.perl6.org, the official Perl 6 documentation.
- List of various Perl 6 learning resources
- 5 to 6 blog articles, for Perl 5 programmers
- [HISTORICAL ARCHIVE] Perl 6 design documents