There is no control over the appearance of the Buttons in the bottom
       Frame nor is there any way to control the placement of the two Frames
       with respect to each other.

##</code><code>##

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

my $tl;
my $mw = MainWindow->new;
$mw->title( "MainWindow" );
$mw->Button( -text => "Toplevel", -command => \&do_Toplevel )->pack();

MainLoop;

sub do_Toplevel {
        if ( !Exists( $tl ) ) {
                $tl = $mw->Toplevel();
                $tl->geometry('300x100+100+100');
                $tl->title( "Toplevel" );
                $tl->Button(
                        -text    => "Close",
                        -command => sub { $tl->withdraw }
                )->pack;
        }
        else {
                $tl->deiconify();
                $tl->raise();
        }
}
##############################################################