Get the perl scripts here.
And here's an installation / configuration guide. Please note that the datadirs mentioned in the guide refer to rrd files. Example:
%datadirs = (
'/opt/collectd/var/lib/collectd/rrd/localhost/apache' => '[Apache]',
);
This means: I've got a data source I'm calling Apache, and you can find it in /opt/collectd/var/lib/collectd/rrd/localhost/apache.