How Do I Cache Just the Homepage with Apache .htaccess?

Question

Below is an example on how to cache all files on the server ending in html or htm for 2 hours (7200 seconds). So how would I go about doing this only for the homepage of the website, but not any other URL?

<FilesMatch "\.(html|htm)$">
Header set Cache-Control "max-age=7200, must-revalidate"
</FilesMatch>

I tried a Directory and a Location directive in my .htaccess file on a CentOS 5 Linux distro, but it gave me 500 errors on the website.

Note also this is a PHP website where we're using the RewriteRule trick to give us pretty URLs through the index.php file. So, that may affect how you answer me.