"least surprise" is a powerful consideration.

Then, IMO, it should not do aliasing. Aliasing (in for/foreach/map/grep/values) still surprises people, and it causes bugs. Except for the few 1000s of people who are really, really into Perl, most programmers don't know about aliases, and it will catch them off-guard.

As for given, it will take a long time before given is used by "the masses" (that is, the 995,000 Perl programmers that aren't deeply connected to it). Most of them will never make the connection that given shares features with for. Even if they know about aliasing in for/foreach, I very much doubt they'll be surprised if given doesn't have it.