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


my $mw = MainWindow->new;
$mw->title( "MainWindow" );
$mw->geometry('400x400+30+30');

$mw->Button( -text => "Toplevel", -command => \&do_Toplevel )->pack();

$mw->waitVisibility;

my $tl;
&do_Toplevel; #initialize it in withdrawn state

MainLoop;

sub do_Toplevel {
       
         my $topx = 300;
	 my $topy = 100;

#         print $mw->geometry,"\n";
         my ($xs,$ys,$signx,$xp,$signy,$yp) = 
	 $mw->geometry =~ /(\d+)x(\d+)([+-]+)(\d+)([+-]+)(\d+)/;
#         print "$xs,$ys,$signx,$xp,$signy,$yp\n";
    
         my $xpos = int($xp + $xs/2 - $topx/2);
	 my $ypos = int($yp + $ys/2 - $topy/2);
    
    	if ( !Exists( $tl ) ) {
         $tl = $mw->Toplevel();
         $tl->geometry($topx.'x'.$topy.'+'.$xpos.'+'.$ypos);
	 $tl->title( "Toplevel" );
	 #put all your widgets here
         $tl->Button(
		-text    => "Close",
		-command => sub { $tl->grabRelease;
	                  $tl->withdraw }
		)->pack;
	 $tl->withdraw;
	}
	else {
	        $tl->geometry($topx.'x'.$topy.'+'.$xpos.'+'.$ypos);
		$tl->deiconify();
		$tl->raise();
		$tl->grabGlobal;
	}
}
##############################################################