There is certainly something I still don't understand about the behavour, but since it appears to be a bug in ActivePerl 5.8.7, I'm not going to spend any more time trying to figure it out.
Instead, I'm pursuing the Perl upgrade path, but after a number of
hours trying to get the PAR packager working with the updated Perl,
I still haven't got it running yet. So this may take a while. I'll
let you know when I have something ready.