use strict;
use HTML::Template;

my $data = do {local $/; <DATA>};
my $tmpl = HTML::Template->new(scalarref => \$data);

my $rows = [
   { col1 => 'Graham Chapman', col2 => 'John Cleese'   },
   { col1 => 'Terry Gilliam',  col2 => 'Eric Idle'     },
   { col1 => 'Terry Jones ',   col2 => 'Michael Palin' },
   { col1 => 'Terry Jones ',   col2 => 'Michael Palin' },
   { col1 => 'Terry Gilliam',  col2 => 'Eric Idle'     },
];

my $i = 0;
my @class = qw(one two three);

$tmpl->param(
   rows => [
      map {
         { %$_, class => $class[$i++ % @class] }
      } @$rows 
   ],
);

print $tmpl->output;

__DATA__
<style type="text/css">
<!--
   table    { border-spacing: 0px; }
   td       { padding: 3px; }
   td.one   { background-color: #c0c0c0; }
   td.three { background-color: #e0e0e0; }
   td.two   { background-color: #d0d0d0; }
-->
</style>

<table>
<tmpl_loop rows>
  <tr>
    <td class="<tmpl_var class>">
      <tmpl_var col1>
    </td>
    <td class="<tmpl_var class>">
      <tmpl_var col2>
    </td>
  <tr>
</tmpl_loop>
</table>