my $id = 1;

sub Yes_Mail {
    $main_window->TrayIconMailNo->{-id});
    $main_window->{'TrayIconMailNo'}->DESTROY();
    $main_window->AddNotifyIcon (
        -icon    => $tray_icon_file_mail_yes,
        -id      => $id++,
        -name    => "TrayIconMailYes",
        -tip     => "LupoX POP3 Notifier(TM) - YOU HAVE MAIL"
);

##</code><code>##

my %events = (
    512 => sub { print "mouse over icon\n" },
    513 => sub { print "left button clicked\n"; },
    # et cetera
);

if (exists $events{$msg}) {
    $events{$msg}->();
}

##</code><code>##

open (NEW, 'mail.tmp') or die "Cannot open mail.tmp: $!\n";
if (defined(my $line = <NEW>)) {
    Yes_Mail();
}
close NEW;