Is it possible to stop a signal callback?

["Ye Wenbin" <wenbinye gmail com>]

Hi,
In my application, there is a callback which may take a long time to  
finish.
Is it possible to return from the callback when user really need? For  
example,
code as following, can I press the button 'cancel' to stop the counting?
Is there any document about thread in Gtk2?

use Gtk2 '-init';
use Glib qw(TRUE FALSE);
my $window = Gtk2::Window->new('toplevel');
$window->signal_connect('delete_event' => sub { Gtk2->main_quit; });

my $hbox= Gtk2::HBox->new(FALSE, 0);
my $but;
$but = Gtk2::Button->new('start');
$but->signal_connect(
    'clicked' => sub {
        my $i = 0;
        while ($i < 10) {
            sleep( 1 );
            $i++;
            print "I'm working\n";
        }
        return FALSE;
    }
);
$hbox->pack_start($but, TRUE, TRUE, 5);
$but = Gtk2::Button->new('Cancel');
$but->signal_connect(
    'clicked' => sub {
        die "Stop it\n";
    }
);
$hbox->pack_start($but, TRUE, TRUE, 5);
$window->add($hbox);
$window->show_all();
Gtk2->main;


--
Best regards,
Ye Wenbin