Making the Right redirect for multilingual sites

The question is this.

There is a site, which is available in several locations (in domenah.rf,. Ru,. Co.za).
Have two language website, which are switched on adding / en or / ru

There is a task to make sure that when you go to their website at site.co.za and www.site.co.za occurs once redirected to site.co.za / en

In. Htaccess is the condition:

RewriteCond% {HTTP_HOST} ^ www.site.co.za $
RewriteRule ^ (. *) $ site.co.za / en / $ 1 [R = 301, L]

In this case, if you add the same address for RewriteCond whi WWW, then we get an infinite loop.

Please tell me how to organize such a redirect.