Just wanted to say a belated "Thanks!" for your explanation, Joost. (I assumed I'd be emailed if anyone responded to my post, and no emails arrived so I assumed no-one had responded; just came wandering back today! My bad.)

While your explanation makes some sense, behaviour like what I described causes me to wonder about the designers of Perl: it seems like whenever they see an opportunity to implement something simply, cleanly and orthogonally, they do it the other way.

Many thanks,
JRH