There is a Perl module NET::IRR. That is what I switched to for IPv6 support after using IRRPT for a few years. IRRPT has been rewritten in Python but have not had time to play with. It includes IPv6 support. You probably have to modify it to output in XR's set format. That's what I did with the original IRRPT.
http://search.cpan.org/~tcaine/Net-IRR/lib/Net/IRR.pm
https://github.com/ktims/irrpt-ng
Courtney Smith
courtneysmith@comcast.net
I wanna devise a virus
To bring dire straits to your environment
Crush your corporations with a mild touch
Trash your whole computer system and revert you to papyrus