use strict;
use warnings;

use Tk;

my $mw = MainWindow->new();

$mw->Button(-text => 'Open Toplevel',
    -command => sub {
        my $single_tl = $mw->Toplevel();
        $single_tl->Button(-text => 'Close',
            -command => sub { $single_tl->destroy(); },
        )->pack();
        $single_tl->grab();
    },
)->pack();

$mw->Button(-text => 'Exit', -command => sub { exit })->pack();

MainLoop;