sub show_box_content {
  $shelf_content -> deleteAll;
  my @content = &get_box_content($_[0]);
  my $i = 0;
  
     #styles for the single rows
  my $greyStyle = $shelf_content -> ItemStyle('text', -background => 'lightgrey', -font => 'Arial 8 bold', -foreground => 'black');
  my $defaultStyle = $shelf_content -> ItemStyle('text', -font => 'Arial 8 bold', -foreground => 'black');
  #give a value for shelf-hlist 
  for (@content) {
    #print "Boxdate: $content[$i][0]\nBoxname: $content[$i][1]\nBoxdescribe: $content[$i][2]\n";
    $shelf_content -> add($i, -data => $content[$i][2]);
    $shelf_content -> itemCreate($i, 0, -text => $content[$i][0], -style => ($i % 2) ? $defaultStyle : $greyStyle);
    $shelf_content -> itemCreate($i, 1, -text => $content[$i][1], -style => ($i % 2) ? $defaultStyle : $greyStyle);
    
    $i++;  
  } 
} #show_box_content

my $hlist = $main -> HList(-sizecmd => sub{&resize});
...

sub resize {
...
}

my $hlist = $main -> HList(-sizecmd => [\&resize,$hlist]);

sub resize {
  my ($hlist) = @_;
  print $hlist->width();
}