tax_query operator woes

I’m not sure that there is a way to get it to use ‘OR’ instead of ‘AND’. Alternatively, you can do:

$myquery['tax_query'] = array(
    'relation' => 'OR',
    array(
        'taxonomy' => 'regions',
        'terms' => array('region1'),
        'field' => 'slug',
        'operator' => 'IN'
    ),
    array(
        'taxonomy' => 'population',
        'terms' => array('pop1'),
        'field' => 'slug',
        'operator' => 'IN'
    ),
    array(
        'taxonomy' => 'population',
        'terms' => array('pop2'),
        'field' => 'slug',
        'operator' => 'IN'
    )
);

query_posts($myquery);