#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 -->