Most interesting and as usual I have to bow before your superior knowledge of these things.
I will just add that I never saw the memory used by my Perl scripts get released back to the OS, but that may say more about my scripts than anything else. I have few long running scripts (except some mod_perl applications) so that may be the reason and I try to be parsimonious with memory so there is probably never enough in one block that can get released back to the OS.
A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James