This works, use the listvariable option instead of insert.

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


my $lst_properties;
my $chk_options;
my $chkoptions;
my $MainWindow;

&maingui;

sub maingui {

    $MainWindow = MainWindow->new(-title=>'Listbox');

my @properties = ("People","Animals","Aliens","Meat",
            "Fruit","Vegies","Dairy","Pultry",
            );

    $chk_options = $MainWindow -> Checkbutton ( -anchor=>'nw',
            -justify=>'left',-relief=>'flat',
            -indicatoron=>1,-text=>'Additional Criteria',
            -variable=>\$chkoptions, -state=>'normal',
            -command=>\&Additional_Criteria
            ) -> grid(-row=>1,-column=>0,-pady=>5);

    $lst_properties= $MainWindow -> Scrolled ( 'Listbox',
            -selectmode=>'single', 
            -relief=>'sunken',
            -scrollbars=>'osoe',
            -width=>50,
            -listvariable=>\@properties,
            -state=>'disabled'
            );


    $lst_properties -> grid(-row=>5,-column=>1,-pady=>3);
   
 MainLoop;
}


sub Additional_Criteria
{
 #code her to test if check box is selected or not

   if ($chkoptions) {
      print "Enable\n";
      $lst_properties->configure(-state=>'normal');
   }
   else {
      print "Disable\n";
      #Code here to DISABLE ListBox
    $lst_properties->configure(-state=>'disabled');
   }
}
[download]