use Win32::GUI;

my $main = Win32::GUI::Window->new();

my $icon = Win32::GUI::Icon->new('test.ico');

my $tray = $main->AddNotifyIcon(
    -name    =>    'tray',
    -icon    =>    $icon,
    -id		=>    0,
    -tip    =>    'icon1'
);

sleep 5; # hover mouse over icon to see tooltip

undef $tray; # try and get rid of old icon

$tray = $main->AddNotifyIcon(
    -name    =>    'tray',
    -icon    =>    $icon,
    -id		=>    0,
    -tip    =>    'icon2'
);

sleep 5; # hover mouse over new icon again