add_action( 'init', function() {
    if ( empty( $_GET['bulk-assign-type'] ) || ! current_user_can( 'administrator' ) ) {
        return;
    }

    $listing_type = 'event'; // modify this
    $listings = (array) get_posts( [
        'post_type' => 'job_listing',
        'posts_per_page' => -1,
        'post_status' => 'any',
    ] );

    foreach ( $listings as $listing ) {
        update_post_meta( $listing->ID, '_case27_listing_type', $listing_type );
    }
} );