I'm using mod_rewrite to virtually map to a local path.

path:
/home/user/subdomain.domain.com/

Rules: 
RewriteEngine On
RewriteCond %{HTTP_HOST} \.([^.]+\.[^.]+\.[^.]+)$
RewriteRule ^(.*) http://%1$1 [R,L]
VirtualDocumentRoot /home/user/%0

[download]
RewriteCond %{HTTP_HOST} \.([^.]+\.[^.]+\.[^.]+)$ will redirect http://www.subdomain.domain.com to http://subdomain.domain.com, but I want the reverse. http://subdomain.domain.com redirected to http://www.subdomain.domain.com and 'www' url to remain unchanged.
Changing the rule to RewriteRule ^(.*) http://www\.%1$1 [R,L] will broke entire configuration. I have also tried to modify RewriteCond %{HTTP_HOST} \.([^.]+\.[^.]+\.[^.]+)$ in many ways, but I don't know how to solve it.
Any help would be greatly appreciated. Thank you!!

In reply to (OT) mod_rewrite anyone? by mrc

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