I just finished gappling with the change-of-systray-icon problem, and here is a short version of what i did :

use Win32::GUI;
use strict;

my $okIcon = new Win32::GUI::Icon('C:\Monolith.ico');
my $badIcon = new Win32::GUI::Icon('C:\Skull & Crossbones.ico');


my $main = Win32::GUI::Window->new(-name => "Main",-size => [250,350])
+;

$main->AddButton(-pos => [10,10],-name => "Bar",-text => "Bad Icon");
$main->AddButton(-pos => [10,35],-name => "Bar2",-text => "Good Icon")
+;

$main->AddNotifyIcon(
        -name => "Tray",
        -tip  => "Tray",
        -icon => $okIcon,
        -id   => 222,
    );


$main->Show();
Win32::GUI::Dialog();


sub Bar_Click {
    Win32::GUI::NotifyIcon::Modify(
         $main, 
         -id => 222, 
         -icon => $badIcon, 
         -tip => "Bad",
    );
}

sub Bar2_Click {
    Win32::GUI::NotifyIcon::Modify(
         $main, 
         -id => 222, 
         -icon => $okIcon, 
         -tip => "OK",
    );
}

sub Main_Terminate {
    $main->AddNotifyIcon(
        -name => "Tray",
        -tip  => '',
        -icon => '',
        -id   => 222,
    );
    -1;
}

sub Main_Minimize {
    $main->Disable();
    $main->Hide();
    1;
}

sub Tray_Click {
    $main->Enable();
    $main->Show();
    1;
}
[download]

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i had a memory leak once, and it ruined my favorite shirt.