Save post meta foreach loop

Question

My brain has fallen over. How do I save this post data? Building some key-value pairs in the form.

    for ($i = 1; $i <= 3; $i++) {
        $saved = $meta[$i];
        //print_r($saved);
        //echo $saved['key'];
        echo '<p>';
        echo '<label for="meta_k_'.$i.'">Key</label> ',   '<input id="meta_k_'.$i.'" type="text" name="_meta['.$i.'][key]" value="'.$saved['key'].'" />&nbsp;&nbsp;';
        echo '<label for="meta_v_'.$i.'">Value</label> ', '<input id="meta_v_'.$i.'" type="text" name="_meta['.$i.'][value]" value="'.$saved['value'].'" />';
        echo '</p>';
    }

How do I save them???

    foreach ($_POST['_meta'] as $key => $value) {
        update_post_meta($post_id, $key, $value);
    }