...
@EXPORT    = qw(Exists Ev exit MainLoop DoOneEvent tkinit);
...

##</code><code>##

#!/usr/bin/env perl

use strict;
use warnings;

use Tk;

my $mw = MainWindow->new;

$mw->Button(-text => 'Exit', -command => sub { exit })->pack;
$mw->Button(-text => 'Destroy', -command => sub { $mw->destroy })->pack;

MainLoop;

print "After MainLoop\n";

##</code><code>##

$ pm_tk_exit_vs_destroy.pl  # Using 'Exit' button
$ pm_tk_exit_vs_destroy.pl  # Using 'Destroy' button
After MainLoop
$