htaccess question

Hay, In Plesk it gives me the ability to add a subdomain to a domain say x开发者_StackOverflow.y.com, the problem is that www.x.y.com gets treated as another subdomain. Is there a way to direct all traffic from www.x.y.com to x.y.com? I tried doing this in php using the 300 header, but stuff like www.x.y.com/mypage, doesn't get redirected. Could i use the .htaccess file to redirect all this traffic?

Thanks

# you probably want www.example.com to forward to example.com -- shorter URLs are sexier.
# no-www.org/faq.php?q=class_b
<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteCond %{HTTPS} !=on
  RewriteCond %{HTTP_HOST} ^www\.(.+)$ [NC]
  RewriteRule ^(.*)$ http://%1/$1 [R=301,L]
</IfModule>

Source: http://html5boilerplate.com

Options +FollowSymlinks
RewriteEngine on
rewritecond %{http_host} ^www.domain.com [nc]
rewriterule ^(.*)$ http://domain.com/$1 [r=301,nc]

From: http://www.webconfs.com/how-to-redirect-a-webpage.php

RewriteEngine On
RewriteCond %{HTTP_HOST} ^www.x.y.com [NC]
RewriteRule ^(.*)$ http://x.y.com/$1 [R=301,L]