my (@diff, @only_array_1, @only_array_2);
my (%h1, %h2);

$h1{$_} = 1 foreach (@erg1);
$h2{$_} = 1 foreach (@erg2);
 
a1: foreach my $k1 (keys %h1) {
 if( exists $h2{$k1}) {
  push @diff, $k1;
  delete $h2{$k1};
  next a1;
 }
 push @only_array_1, $k1;
}
#$listbox_right->insert('end', sort @diff); # hier gibt er mir wieder nutzlose Werte aus
$listbox_right->insert('end', "=============Only User 1===================================");
$listbox_right->insert('end', sort@only_array_1);
$listbox_right->insert('end', "==============Only User 2==================================");
$listbox_right->insert('end', sort keys %h2);
$listbox_right->insert('end', "===========================================================");