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

my $notification = tkinit;
$notification->geometry('+400+400');

# here you can put stuff you want to occur when the window closes
# like send an email or something
#$notification->protocol('WM_DELETE_WINDOW' => sub {   });        

$notification->overrideredirect(1);    # Remove window decorations

$notification->Label(
    -text       => 'Your message displayed here for 5 seconds.',
    -foreground => 'white',
    -background => 'black',
    -height     => 5
)->pack;

$notification->after( 5000, sub{
    $notification->exit;
} );

MainLoop;