Works For Me:

use CGI qw(:standard);

my @headers = ( th('a'),th('b'),th('b'), );
my @row    = ( td('1'),td('2'),td('3'), );

print table(
    thead( Tr( @headers ) ),
    tbody( Tr( @row ) ),
);
[download]

output:

    <table>
        <thead>
            <tr>
                <th>    a
                </th>
                <th>    b
                </th>
                <th>    b
                </th>
            </tr>
        </thead>
        <tbody>
            <tr>
                <td>    1
                </td>
                <td>    2
                </td>
                <td>    3
                </td>
            </tr>
        </tbody>
    </table>
[download]

It's not a matter of slipping thead/tbody in, it's a matter of wrapping them around the outside.

But as everyone else says I'd use templating instead.