Since 5.12, use 5.012; could also introduce changes in behaviour. I'm not too fond of that
Since 5.10, actually. If there was no change in behaviour, there wouldn't be need for the features pragma at all.
$ perl -e'sub say { print "foo\n"; } say for "bar";'
foo
$ perl -E'sub say { print "foo\n"; } say for "bar";'
bar
It was always safe to try
It's no more or less safe to try now as then. By switching use 5.008; for use 5.006;, you could get bugs that changed behaviour and compile-time errors just like you do now.
Update: Deleted a comment based on something I misread.
