#! perl
use strict;
use warnings;

{
    package Foo;

    sub new
    {
        return bless {};
    }

    sub DESTROY
    {
        print "Foo::DESTROY\n";
    }
}

my  $foo = Foo->new();
bar($foo);
print "Back in main\n";

sub bar
{
    print "Begin bar()\n";
    undef $_[0];
    print "End bar()\n";
}

##</code><code>##

 3:14 >perl 556_SoPW.pl
Begin bar()
Foo::DESTROY
End bar()
Back in main

 3:18 >