#!/usr/bin/perl

use strict;
use Tk;
use threads qw(yield);
use threads::shared;

my $win = MainWindow->new();

my $t = threads->new(\&kind);

sub kind {
    sleep(3);
    eltern("hallo Mama");
    return;
}

sub eltern {
    $win->configure(-title=>"$_[0]");
}

MainLoop;

Tk::Error: Can't call method "Call" on an undefined value at C:/Perl/site/lib/Tk
/After.pm line 89.
 [once,[{},after#1,idle,once,[ConfigChanged,{},{}]]]
 ("after" script)