#!/usr/local/bin/perl -w
use strict;
use Tk;
my $mw = MainWindow->new;
my $text = '0123456789';
my $e  = $mw->Entry(-validate => 'all', -textvariable => \$text,
                    -vcmd => \&validate,
                    -invcmd  => sub { $mw->bell })->pack;
my $l  = $mw->Label(-textvariable => \$text)->pack;
$mw->Button(-text => 'Set',  -command => sub { $text = '0123456789' })->pack;
$mw->Button(-text => 'MisSet',  -command => sub { $text = 'A012345678' })->pack;
$mw->Button(-text => 'Quit', -command => [destroy => $mw])->pack;
MainLoop;
sub validate
{
 my @args = @_;
 foreach (@args)
  {
   $_ = defined ($_) ? "'$_'" : 'undef';
  }
 print 'validate ',join(',',@args),"\n";
 return $_[0] =~ /^\d*$/;
}