use Tk;

my $mw = MainWindow->new();

$mw->send('Foo' => $file_name);

##</code><code>##


use Tk;

my $main_window = MainWindow->new(-title => 'My other prog');
$main_window->appname('Foo');

MainLoop;

sub Tk::Receive{
    shift;
    my $string = shift;

    if ($string =~ /pattern/){
       # Do somthing.    
    }
    else { die 'Wrong arg Received'}
}