[CentOS] apache redirect rule

Hello guys,

sorry for this OT, but It seems that I am a very stupid :(.
I want to achieve one simple think in apache 2.2.

If users will type extensions.polarion.com I want to redirect him to
extensions.polarion.com/polarion/extensions However there are
following rules that apply

1) extensions.polarion.com is an virtual host alias to
community.polarion.com . There is a definition inside virtual host
which redirects all / to /polarion using this RedirectMatch permanent
^/$ /polarion/

2) what I want to achieve is to check if user comes from
extensions.polarion.com and If so to redirect him to
extensions.polarion.com/polarion/extensions

I guess something like :

RewriteCond %{HTTP_HOST} extensions.polarion.com
RewriteRule / http://extensions.polarion.com/polarion/extensions/

Is this going to work?

Thanks milion times.

David