<TMPL_LOOP OUTER_LOOP>
      OUTER: <TMPL_VAR OUTER_VAR>
        <TMPL_LOOP INNER_LOOP>
           INNER: <TMPL_VAR INNER_VAR>
           INSIDE OUT: <TMPL_VAR OUTER_VAR>
        </TMPL_LOOP>
   </TMPL_LOOP>
[download]

<select>
<tmpl_loop loop_one>
<option name='<tmpl_var name>'> <tmpl_var value> </option> 
      <tmpl_if loop_two>
      <tmpl_loop loop_two>
 <option name='<tmpl_var name_one>'> <tmpl_var value_one>  </option>
      </tmpl_loop>
       </tmpl_if>
</tmpl_loop>
</select>
[download]

my (@loop_two,@loop_one);

for(@arr_name) {
   push @loop_two, {
                      name_one => 1,
                      value_one => 2 
                   };

}

for(@arr_one) {
   push @loop_one, {
                     name => 1,
               value => 2,
             loop_two => \@loop_two 
                   };
}

$html->param(loop_one => \@loop_one);

return $html->output();

where $html is HTML::Template object.
[download]

#test.pl:
use HTML::Template;
my $tmpl = HTML::Template->new(filename => 'test.tmpl');
$tmpl->param( Loop1 => [
        { Loop2 => [ {name => "me"}, {name=>"another"}  ] },
        { Loop2 => [ {name => "you" } ] },
]);
print $tmpl->output();

# and test.tmpl.
<!-- TMPL_LOOP NAME=Loop1 -->
  <!-- TMPL_LOOP NAME=Loop2 -->
       <!--TMPL_VAR NAME = name -->
  <!--/TMPL_LOOP -->
<!--/TMPL_LOOP -->
[download]