#!/usr/bin/perl
use warnings;
use strict;
use Tk;
use Tk::NoteBook;

my $mw  = new MainWindow;

my $note = $mw->NoteBook( )->pack(
   -side   => "left",
   -fill   => "both",
   -expand => 1
);
   my $page1 = $note->add("1", -label => 'Haupt');
   my $page3 = $note->add("2", -label => 'Einstellungen');
   my $page2 = $note->add("3", -label => 'Material');
   my $page4 = $note->add("4", -label => 'Ergebnis');

my $start  = $mw->Button( -text => "Start", -command => sub { 
  $note->raise( 3 );
  ∋
})->pack;

MainLoop;
sub ni{
        sleep(1);
	print "huhu";
}