use strict;
use warnings;

use Tk;

my ($mw,$EntryBox1,$EntryBox2,$variable1,$variable1_previous,$variable2);

$mw = MainWindow->new;
$EntryBox1 = $mw->Entry(-textvariable => \$variable1,
		)
		->place(-relx => 0.06, -rely => 0.03);

$EntryBox2 = $mw->Entry(-textvariable => \$variable2,
		)
		->place(-relx => 0.06, -rely => 0.20);

$EntryBox1->bind("<FocusIn>",\&save_previous_value);
$EntryBox1->bind("<FocusOut>",\&compare_values);

MainLoop;

sub save_previous_value {
$variable1_previous = $variable1;
      }

sub compare_values {
if ($variable1 ne $variable1_previous) {
$mw->messageBox(-message => "The value has been changed.",-type => "ok");
       }
       }