#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = new MainWindow;
$mw->title("Close test");
$mw->geometry("400x250");

#prevents mw from closing 
$mw->protocol('WM_DELETE_WINDOW' => sub {
                print "do stuff here before the exit\n";
                exit;
           });

MainLoop;