I think the important thing is to consider just how costly the other options are. I'm no expert when it comes to GC, but there are a myriad of options available and I think that timely destruction has one particular benefit: consistancy.

The timely deterministic options (which, in a language with references, is singular--refcounting) are expensive, both in processor time and in programming time. Also rather error-prone, unfortunately.

They also don't guarantee consistency, though they do guarantee determinism. Not that you're necessarily going to guess the time right, but you've a reasonably good chance.

To take one particular operation and declare "This could happen at any old time" instantly puts the programmer into headache mode"

That's always true, though. Perl is sufficiently introspective, and is getting more introspective, to make timing of destruction potentially indeterminate. And most objects don't have DESTROY methods. Just wait until we start throw

I see little choice but to make timely GC an option, but I am confident that there is enough collective brainpower available to make it efficient as an option under reasonable circumstances.

Thanks for the vote of confidence, bu I should point out that I am the brainpower in this case, along with a stack of books and papers by people rather more clever than I am. If it was easy or inexpensive to do this, I wouldn't be asking the question.