my $w;
$w->{main} = MainWindow->new;
$w->{other_widgets} = $w->{main}->Label->....
# and then later...
&subroutine($w);

sub subroutine
{
    my $w = shift;
    # Do stuff with $w here now like normal
    $w->{main}->configure( -title => "new title" );
}

##</code><code>##

1 if $a; # for example

##</code><code>##

sub unused
{
    warn "sub unused was used!!!\n";
    return;
    1 if $a;
    1 if $b;
}

##</code><code>##

#! /usr/bin/perl -w

use strict;
use Tk;
use Tk::Toplevel;

################
# Main Routine #
################

my $w;

$w->{main} = MainWindow->new(-title => 'Tk Hash');
$w->{main}->Button(-text => "Click me to open a new toplevel", -command => [ \&new_tl, $w ])->pack;
$w->{main}->Button(-text => "Click me to test for other button", -command => [ \&test_tl, $w ])->pack;

MainLoop;

exit;

###############
# Subroutines #
###############

sub new_tl
{
	my $w = shift;

	if ( not Tk::Exists $w->{toplevel} )
	{
		$w->{toplevel} = $w->{main}->Toplevel( -takefocus => 1, -title => 'Top Level' );
		$w->{testbutton} = $w->{toplevel}->Button(-text => 'Null button');
	}
	else
	{
		$w->{toplevel}->deiconify();
		$w->{toplevel}->raise();
		$w->{toplevel}->focusForce();
	}
}

sub test_tl
{
	my $w = shift;

	if ( Tk::Exists $w->{testbutton} )
	{
		print "testbutton exists\n";
	}
	else
	{
		print "testbutton does not exist\n";
	}
}