That is clever, but is it needed?

as far as I can tell, it isn't needed, as the messagebox pops up on top of the notification no matter what happens

#!/usr/bin/perl --
use strict; use warnings;

use Tk;

Main( @ARGV );
exit( 0 );

sub Main {
    my $mw = tkinit( );
    $mw->geometry('+300+400');
    
    my $notification = $mw->Toplevel( );
    $notification->geometry('+400+400');
    $notification->overrideredirect(1);    # Remove window decorations
    $notification->withdraw;               # Hide display window
    $notification->Label(
        -text       => 'keep clicking toggle ',
        -foreground => 'white',
        -background => 'black',
        -height     => 5
    )->pack;

    $notification->Button(
        -text    => 'Press Me',
#~         -command => [ \&important_message, $notification ], ## not 
+needed
        -command => \&important_message,
    )->pack;
    
    $mw->Button(
        -text    => 'Display Notification Window',
        -command => [ 'deiconify', $notification ],
    )->pack->focus;
    $mw->Button(
        -text    => 'toggle topmost notification ',
        -command => [ \&toggle_topmost , $notification ],
    )->pack;
    $mw->Button(
        -text    => 'hide notification ',
        -command => [ 'withdraw', $notification ],
    )->pack;
    
##    $mw->WidgetDump; ## debugging aid
    MainLoop;
}

sub important_message {
#~     my( $n ) = @_;
    my( $n ) = $Tk::widget;
#~     my $msg = $mw->messageBox( ## works to raise above $notificatio
+n on win32, might not work on all platforms
    my $msg = $n->messageBox(
        -icon => 'error', 
        -message => "No tests selected", 
        -title => 'Error', -type => 'Ok', 
        -default => 'Ok',
    );
}
sub toggle_topmost {
    my( $n ) = @_;
    warn $n->attributes;
    $n->attributes(-topmost => ! $n->attributes(-topmost ) );;
    $n->parent->raise;
    $n->parent->focus;
}

__END__
__END__
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