How to force toplevel->show

[<poyen aleks com>]

Hi all ,

 How can I force Gtk to have my window showed when I want ?
 Here is my case : I create a window, make a window->show on it,
and THEN, start a while loop. The windows shows itself only AFTER the
loop. That's why I think I'd better force the window to be showed :

Here is my code :

my $win = new Gtk::Window ;
        $win->show_all ;
        print " See the window ? \n" ;
        #At that point , no !
        my $i = 100000 ;
        while ($i) {print "."; $i-- };
        # Here, the $win displays itself at last.

I've not seen any other functions, like the Gtk::Gdk->flush that would
apply  for Gtk::Window.

If not found anything like that in the cookbook.
Thanks if you have any tips.