wordpress:snippet:query args by first initial of lastname

wp-first-initial-sort.php

<?php
    $args = array(
        'post_type' => 'this-post',
        'meta_query' => array(
            array(
                'key' => 'this-post-last-name',
                'value' => array( 'L', chr(ord('L')+1) ),
                'orderby' => 'meta_value',
                'compare' => 'BETWEEN',
                'order' => 'ASC'
            ),
            array(
                'key' => 'this-post-last-name',
                'value' => chr(ord('L')+1),
                'orderby' => 'meta_value',
                'compare' => '!='
            )
        )
    );
    $query = new WP_Query( $args );
 ?>