You right. You missed something. Here small part from HTML::Template docs:

 In the template:
   <TMPL_LOOP NAME=EMPLOYEE_INFO>
      Name: <TMPL_VAR NAME=NAME> 

      Job:  <TMPL_VAR NAME=JOB>  

   </TMPL_LOOP>
 In the script:

$template->param(EMPLOYEE_INFO => [ 
                                       { name => 'Sam', job => 'progra
+mmer' },
                                       { name => 'Steve', job => 'soda
+ jerk' },
                                     ]
                   );
print $template->output();
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So you need array of hashes. If you show more code we can help you.

As Fletch suggest you need

$template->param( 'HTMLloop' => \@array );
or
$template->param( 'HTMLloop' => [ @array ] );
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Where @array consists of hash refs.

Ok, here's what I got so far.

     foreach my $Temp (@IsNew){
       my %param_2 = (
          'Flag'=>$Temp,  #<-- TEST
          );

       foreach my $product (@Products) {
        my %param = (
          'Code'=>$product,
        }
        push(@loop_data_1, \%param);
       }

      $loop_data_3{$counter} = @loop_data_1;
      $param_2{'ProductList'} = \$loop_data_3{$counter};
      push(@loop_data_2, \%param_2);
      @loop_data_1 = ();
     }

     $tmpl->param('NumOfProductLists'=>\@loop_data_2);
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@loop_data_1 contains the data for the inner loop
@loop_data_2 countain the data for the superior loop (inside it should be arbitray number of different @loop_data_1 arrays). Basically i want to dinamicly add drop down boxes with different \<selected\> elements. That's why I think I need a different @loop_data_1 for each @loop_data_2.

This is where I thought of using or an array of arrays or a hash of arrays...

I'm think this is wrong (it's looks very strange for me):

$loop_data_3{$counter} = @loop_data_1;
$param_2{'ProductList'} = \$loop_data_3{$counter};
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Maybe you want:

$loop_data_3{$counter} = \@loop_data_1;
$param_2{'ProductList'} = $loop_data_3{$counter};
[download]