Expanding a bit further.

That comment only applies to mark-and-sweep type garbage collection. As a general rule, Perl's reference-counted garbage collection is deterministic and mostly handles as you would expect. (Present case excepted, of course.)

Personally, I regret the loss of a defined, consistent object lifetime caused by using mark-and-sweep. Having the lifetime of a object determine the timing of events is quite useful. It's one of the reasons I prefer Perl and C++ to Java.

case in point:

package H;
sub DESTROY { print "DESTROY\n"; }

sub new { my $class = shift; bless {}, $class; }

{
    if(my $h = H->new()) {
        print "IN\n";
        undef $h;
    }
    print "\$h out of scope\n";
}
print "why now?\n";
[download]

produces:

IN
DESTROY
$h out of scope
why now?
[download]

As does:

package H;
sub DESTROY { print "DESTROY\n"; }

sub new { my $class = shift; bless {}, $class; }

{
    {
        if(my $h = H->new()) {
            print "IN\n";
        }
    }
    print "\$h out of scope\n";
}
print "why now?\n";
[download]