I did this using nested loops, but that means you'll need to transform your array into rows of columns as described in other replies.

My code received a single array of products and turned it into rows of three product elements each. It works thusly:

my @rows;
while (@products) {
    push @rows,
    {
     'loop_products' => [splice @products, 0, 3],
    };
}
$template_body->param(
   loop_row => \@rows,
   );
[download]

Then in your template, you loop through both arrays:

<TMPL_LOOP NAME=loop_row>
   <TMPL_LOOP NAME=loop_products>
       Display one product here.
   </TMPL_LOOP>
</TMPL_LOOP>
[download]

Works fine if your columns flow across the row. Enjoy :)