#!/usr/bin/perl -w
use strict;
use Tk;

my $mw = tkinit();
my @werte = qw(1 2 3 4 5 6);
my $listbox = $mw->Scrolled('Listbox',
                           -scrollbars => 'e',
                           -height => 5,
                           -listvariable => \@werte, -exportselection => 1,)
                 ->pack(-side => 'left', -fill => 'y',);
$listbox->bind('<<ListboxSelect>>', sub{check_state()} );

my $b1 = $mw->Button(-text => 'test')->pack;

my $lb2 = $mw->Scrolled('Listbox',
                        -scrollbars => 'e',
                        -height => 5,
                        -listvariable => \@werte,)
             ->pack(-side => 'left', -fill => 'y',);
$lb2->bind('<<ListboxSelect>>', sub{check_state()});

MainLoop;

sub check_state {
  if ($listbox->curselection()) {
    $b1->configure( -state => "normal");
  } else {
    $b1->configure( -state => "disabled" );
  }
}