RewriteEngine On
RewriteCond %{HTTP_HOST}        !^myhostname.com$
RewriteRule ^/support(/|$)      http://myhostname.com%{REQUEST_URI} [R,L]

<VirtualHost myotherhostname.com:80>
...
    RewriteEngine On
    RewriteOptions inherit
    RewriteCond /my/document/root%{REQUEST_FILENAME} !-f
    RewriteCond /my/document/root%{REQUEST_FILENAME} !-d
    RewriteRule ^/(.*)  /cgi-bin/script.pl/$1 [PT]
...