Stanislav,
I am not sure moritz's answer explained things completely. If you understood great. If not (for those following along at home), here is more of the story. Unlike perl 5, perl 6 will not be specification by implementation. It has an independent specification and any implementation that passes the perl 6 test suite will be consider perl 6. While the perl 6 specification is still changing (very slowly - more fine tuning at this point), there are a number of implementations that are in various stages of completion. The Rakudo (perl 6 on parrot) implementation is not yet meeting the spec in this regard. That's the simple answer.

See Getting Involved with Perl 6 - an Update for more information.