use warnings;

 use strict;
 
 use Tk;
 use Tk::HList;
 #
 # MainWindow
 #
 my $mw = MainWindow->new;
 #
 # Menu
 #
 my $m = $mw->Menu(qw/-type menubar/);
 $mw->configure(-menu => $m);
 
 my $ma = $m->cascade(-tearoff => 0, -label => '~Ansicht');
 
 my $pr_sicht = 1;
 
 #
 # PanedWindow
 #
 my $panel = $mw->Panedwindow(qw/-orient horizontal/)->pack;
 
 my $fr_left = $mw->Frame->pack;;
 my $fr_right = $mw->Frame->pack;
 
 $panel->add($fr_left, $fr_right);
 
 my $hlist = $fr_left->HList(qw/-bg white/)
         ->pack(qw/-expand yes -fill both/);
 
 my $data  = $fr_right->Canvas(qw/-bg white/)
         ->pack;
 
 $ma->checkbutton(
         -label => 'Projekt-Explorer',
         -variable => \$pr_sicht,
         -command => sub {
                  unless( $pr_sicht ){
                     $panel->forget($fr_left);
                  }
                  else{
                     $panel->add($fr_left,-before => $fr_right);;
                  }
 
         }
 );
 
 MainLoop;