I see little point in versioning or emulation until we have spec versions and complete test suite versions that can validate them. And I see no need to "practice" versioning before that happens; it will just slow down the drive to complete 6.0.0, and there will (I hope) be time to consider the finer points of API versioning between 6.0 and 6.1. (I am presuming that 6.0.1+ are just bugfix releases.)
Until 6.0.0, there is *no* guarantee of stability. You are all Early Adopters. If you can't figure out how to snapshot a particular version and keep it around, you probably shouldn't be Early Adopting. The whole point of Rakudo * is to give us lots of Early Adopters so we can put lots of final polish onto 6.0.0 as rapidly as possible after that. Don't start asking us to leap across the chasm before we're ready. So let's try to avoid the backwards compatibility prison of Perl 5 at least until 6.0.0 comes out--the poor persecuted Perl 6 developers have it hard enough as it is. Most of them already ignore most of perl6-language most of the time because most of the discussion here is not terribly relevant to most of what they have to do right now. And most of the nitty-gritty design work is actually happening on IRC these days, in direct response to the implementors woes. Blue sky notions are fine here, but please realize that that is what they are, and please don't torment my developers any more than I'm already tormenting them. :) Larry
