use strict;
use threads; 

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

sub kind {
    my $var = 0;
    while(1) {
        $var++;
        fertig($var);
        last if $var == 10;
    }
    return 0;
}

sub fertig {
             # hier steht nichts drin
}

       Can't undef active subroutine
           (F) You can't undefine a routine that's currently run-
           ning.  You can, however, redefine it while it's run-
           ning, and you can even undef the redefined subroutine
           while the old routine is running.  Go figure.

#!/usr/bin/perl

use strict;
use threads; 
use Tk;

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


sub kind {
    #
}
$th_inc->join();

#!/usr/bin/perl

use strict;
use threads; 


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

$th_inc->join();

sub kind {
    sleep(4);
    print "Kind ist fertig\n";
    exit;
}
print "Vater fertig\n";

use warnings;
use strict;
use threads;

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

sub kind {
    print "hi";
    exit;
}