use strict;
    use warnings;
    use 5.012;
    use Tk;
    use Tk::DialogBox;

    my $mw = MainWindow->new;
    $mw->geometry('200x200+-300+300');    # Note the -300 horiz coord

    $mw->DialogBox(-buttons => [ 'OK' ])
    ->Show(-popover => $mw);

    MainLoop;