If I'm not mistaken, I believe that there's another issue you're trying to pull it here, namely difference between for(1) and for(1..3). They _do_ behave weirdly, I totally agree. But I believe that's a totally separate issue, probably related to parser even, because this code:
Sorry, I didn't make myself clear. I do see that these values are modifiable. But my objection is that for(1..3) construct doesn't do aliasing, which is 50% of the original bug. If my example above did print 3 instead of 2, then yes, I'd accept that as a proof.
Same thing on $_++ for 1 - it dies, because of aliasing comes into play. And I neither get what does "intentionally returns a modifiable value (in a sense) some of the times" mean. For what I see, it just doesn't return a modifiable value, at all.