Threads and Gtk2

[Javier Godinez <godinezj gmail com>]

Hello,

Is there a way to gracefully stop a thread from a Gtk2 callback by
using a global?
I am not sure how to get out of the running thread as shown here:

#############################
#!/usr/bin/perl -w

use Gtk2 '-init';
use strict;
use threads;

my $keep_running = 1;
my $thr1 = threads->new(sub {

       while ($keep_running == 1 ) {
               print "Hello\n";
               sleep(1);
       }
});

sub button_callback {

       $keep_running = 0;
       $thr1->join;
       Gtk2->main_quit;
}


my $window = Gtk2::Window->new;
my $button = Gtk2::Button->new ("Quit!");
$button->signal_connect (clicked => \&button_callback);

$window->add($button);
$window-> show_all;
Gtk2->main;
#############################
Any help will be greatly appreciated...
Thanks, Javier Godinez