The Shell Script Evidence Source allows you to create any script you want including (but not limited to) perl, ruby, bash or AppleScript as an evidence source for ControlPlane. Any script you write should have an exit status of 0 for success or anything other than 0 for a failure.
An example bash script could be as simple as
#!/bin/bash exit 0
The above script would provide a "true" result to ControlPlane.