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

use Tk;

my $mw  = MainWindow->new();

createWindowandWait();

print "fertig!\n";

Tk::MainLoop();

sub createWindowandWait{
        my $window      = $mw->Toplevel();

        my $ok  = undef;
        $window->Button(
                -text => 'fertig!',
                -command        => sub{$ok = 1;}
        )->pack();

        $window->focusForce();

        # warte solange bis variable '$ok' den wert true hat:
        $window->waitVariable(\$ok);
}