#!/usr/local/bin/perl -w
use Tk;
require Tk::Text;

{
 package Tk::Dwidget;
use base  qw(Tk::Frame);
 Construct Tk::Widget 'Dwidget';

 sub Populate
 {
  my ($cw,$args) = @_;
  $cw->SUPER::Populate($args);
  my $w = $cw->Label(-text => 'A Subwidget')->pack;
  $cw->Advertise('label' => $w);
  $cw->ConfigSpecs(-foreground => [$w,'foreground','Foreground','yellow'],
                   -background => ['METHOD','background','Background','white']
                  );
 }

 sub background
 {
  # print 'background(',join(',',@_),")\n";
  my $w = shift;
  if (@_)
   {
    $w->Subwidget('label')->configure(-background => @_);
   }
  return $w->Subwidget('label')->cget('-background');
 }

}

my $mw = MainWindow->new;
$mw->optionAdd('*Dwidget.Foreground' => 'green');
my $w  = $mw->Dwidget(-bg => 'red')->pack;

$w->repeat(5000,sub { my $fg = $w->cget('-fg');
                      my $bg = $w->cget('-bg');
                      $w->configure(-fg => $bg, -bg => $fg)});

$w->after(4000,sub {$w->configure(-fg => 'blue')});
MainLoop;