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

my $main = MainWindow->new ();
my $dlg = $main->DialogBox (
    -title   => "demo Dialog",
    -buttons => ["OK"]
);

$dlg->add ('Label', -text => <<MSG)->form ();
Click OK to close the dialog.
MSG

$main->withdraw ();
$dlg->transient (undef);
$dlg->Show (-global);