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

use Tk;

my $embCanvas = MainWindow->new;
my $xVConsSflEmbMax0 = 1;
my $xVConsSflEmbMax = $xVConsSflEmbMax0;
my $emb1Entry = $embCanvas->Entry(
      -textvariable     => \$xVConsSflEmbMax,
      -width            => 3,
      -validate         => 'focusout',
      -validatecommand  => sub { warn "@_\n"; $_[0] =~ /^\d*\.?\d+$/ },
      -invalidcommand   => \&invalid,
    )->pack;
my $qb = $embCanvas->Button(
        -text    => 'Quit',
        -command => sub { exit }
        )->pack;

MainLoop();

sub invalid {
    $xVConsSflEmbMax = $xVConsSflEmbMax0;
    $emb1Entry->configure(-validate => 'focusout');
}