uh, override the set method?
Except you have to create a convoluted mess of tying a variable and returning it in a way that is both hard to read and hard to maintain, at the dubious benefit of having sugar that is not socially acceptable *ANYWAY* in perl today.
What is the point of your discussion? Are you proposing to revise the currently unversally accepted style? Because Perl 6 is already doing that and it will look like you want it to look, except it won't be insane.
If you are trying to fix the accessor code smell (Which is moot in my opinion - accessors are necessary for storing data in a data oriented culture like perl whether the smalltalk heads like it or not) by abusing weird perl features is IMHO not going to give you any less code smell, but actually more (IntentionNotAlgorithm, KeepItSimpleStupid, YouAren'tGonnaNeedIt, FeatureCreep).
Punchline: you're proposing to simplify by making it more complex. That's wrong. I think that this is MentalMasturbation.