The exact same could be said about Perl 6 ;)
Is this really the case?
https://github.com/niner/Inline-Perl5
http://stackoverflow.com/questions/9173043/how-can-i-use-per...
My understanding is that LOTS of Python2 programs work fine in Python3 with no (or very trivial) changes. Very very few Perl5 programs will work fine in Perl6 with no changes.