And, frankly, being able to depend on timely destruction would be nice.

It's a Perl5 feature! Don't know about Perl6.

Destruction of SVs is not related to what has a hard reference (C pointer) to it. As soon all the lexical variables, package variables, stack reference, etc disappear, destruction occurs (including calling the appropriate DESTROY).

use Devel::Peek;

sub DESTROY { print STDERR "*Destroyed*\n" }

{
   local $foo;
   {
      my $bar = bless {};
      $foo = $bar;
      Dump($foo);
      print STDERR ("Exiting inner\n");
   }
   Dump($foo);
   print STDERR ("Exiting outer\n");
}

print STDERR ("Exiting file scope\n");
[download]

Here's the relevant lines of the output:

    REFCNT = 2
Exiting inner
    REFCNT = 1
Exiting outer
*Destroyed*
Exiting file scope
[download]

Re^2: deleteing references might help. It doesn't matter whether a value is referenced by a lexical var, by a package var, or by the underlying memory structure of an array. As soon as something's refcount reaches zero, it is destroyed. In the figure, "Automatically" can be read as "Immediately".