mod_rewrite rewrite_rule syntax question

I have the following in my .htaccess currently-

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule ^go/([^/]*)/([0-9]+)/([0-9]+)/?$ http://foo.com/wp-content/plugins/foo/cloak.php?post_id=$2&link_num=$3&cloaked_url=$0 [L]
RewriteRule ^go/([^/]+)[/]?$ http://foo.com/wp-content/plugins/foo/cloak.php?name=$1&cloaked_url=$0 [L]
</IfModule>

I want to change it so that the domain 'http://foo.com' is auto-detected and inserted (or just left off if it's unnecessary.

I'm hoping to use this .htaccess to manage multiple mapped domains to the same code base and can't really have it work w开发者_StackOverflowith a specific URI in there.

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Use RewriteCond for that:

RewriteCond %{HTTP_HOST} !^foo.com$
RewriteRule ...