Program with Tk::TOTD not exiting properly

[ric00015]

Earlier I asked about how to get a popup screen with help, and a checkbox "Check to show on startup" type thing. I was told about Tk::TOTD, and it works nicely. However, for some reason, when the program ends, it doesn't seem to return control to the shell that called it once the program exits. The effect is reproducible in the following code:

#!/usr/bin/env perl

use strict;
use warnings;
use utf8;
use Tk;
use Tk::TOTD;

my $mw = MainWindow->new;

my $label = $mw->Label(
    -text => 'hi!')->pack;
my $entry = $mw->Entry()->pack;
my $button = $mw->Button(
    -text => 'push me!')->pack;

my @messages = (
    'message 1',
    'message 2',
    'message 3');

my $totd = $mw->TOTD (
    -title    => 'Tip Of The Day',
    -messages => \@messages);

$totd->Show;

MainLoop;