httpd.conf:

<VirtualHost *>
  ServerName durl
  ServerAlias *.durl
  DocumentRoot /home/aneganov/projects/durl
</VirtualHost>

.htaccess:

RedirectMatch preview\.durl http://durl:81/preview.php

hosts:

127.0.0.1 durl preview.durl

== 
This outputs http://durl:81/index.php page either for
  http://durl:81
or for 
  http://preview.durl:81
requests