For my following little program I did no use threads

    use strict;
    use warnings;

    use CProcess; # own class
    use B;

    CProcess->PrintProcessInfo("perl.exe");

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# Output: Process-ID 12280: Memory 13716 KB (+13716 KB) - Peak 13716 KB - Threads 3 - Handles 115 (perl)

The only packages I use are:

use strict;
use warnings;
use Carp;
use FileHandle;
use Sys::Hostname;
use Cwd;
use Win32::Registry;
use IO::Select;
require Win32::Console;
require Win32::Clipboard;
require Win32::PerfLib;
require Win32::OLE;
require Tk::MainWindow;
require 5.000;
require Exporter;
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To count refcounts I use

require B;

    my $anon = [];
    my $otherref = $anon;

    my $refcount =  B::svref_2object($anon)->REFCNT(); # => 2
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which counts the referents of the referenced object (and not only of the variable itself like Devel::Peek)