#! code

To redirect from HTTPS to HTTP on the home page only using the following rule.

RewriteCond %{HTTPS} on
RewriteRule ^/?$ http://%{SERVER_NAME}/ [R=301,L]

The variable %{HTTPS} will be either "on" or "off" and will be enabled even if SSL is not installed on your site. The rule above sees that HTTPS is on and redirects the home page to the HTTP version. You can even chain lots of rules together like this.