You can play some variations of backgammon on TigerGammon. So far it is
Since existing clients do not support these variations, you have to send your invitation for these matches
through the commandline of your browser.
invite <name> <ML> nack↵
invite <name> <ML> hyper↵
to invite your opponent <name> for match up to <ML> of either
nackgammon or hypergammon, respectively.
invite andreas 3 nack↵
invites player andreas to a 3 point match nackgammon.
If you are invited to such a variation, it says It's nackGammon
in your system window.