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

use Tk;

sub show_dialog {
    my ($mw) = @_;
    my $dialog = $mw->Dialog(-buttons => ['OK', 'Cancel']);
    my $lb = $dialog->Listbox(
        -listvariable => my $valid = [ 'valid', 'invalid' ]
    )->pack;

    $dialog->Walk(sub {
        my $widget = shift;
        if ('Button' eq $widget->class && 'OK' eq $widget->cget('-text')) {
            my $orig = $widget->cget('-command');

            $widget->configure(-command => sub {
                if ('valid' eq $valid->[ $lb->curselection->[0] ]) {
                    $orig->[0]->();

                } else {
                    $dialog->Dialog(-title   => 'Invalid',
                                    -text    => 'Invalid',
                                    -bitmap  => 'error',
                                    -buttons => [ 'OK' ]
                                   )->Show;
                }
            });
        }
    });

    $dialog->Show;
}

my $mw  = 'MainWindow'->new(-title => 'Validation');

$mw->Button(-text    => 'Show Dialog',
            -command => [\&show_dialog, $mw])->pack;

$mw->Button(-text    => 'Quit',
            -command => \&Tk::exit)->pack;

MainLoop();


##</code><code>##

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}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,