If you have a Drupal multisite with predictable hostnames, use this to keep your sites.php lean.

sites.php

<?php

$sites['somecustomsitename.com'] = 'somecustomsite.com';

if (strpos($_SERVER['HTTP_HOST'], "-ra") != FALSE) // somesite-ra.com
{
    $sites[$_SERVER['HTTP_HOST']] = // Cut out -ra and rewrite to somesite.com
        str_replace("-ra", "", $_SERVER['HTTP_HOST']);
}

if (strpos($_SERVER['HTTP_HOST'], "-dev") != FALSE) // somesite-dev.com
{
    $sites[$_SERVER['HTTP_HOST']] = // Cut out -sites and rewrite to somesite.com
        str_replace("-dev", "", $_SERVER['HTTP_HOST']);
}