Is it required to destroy the PDF object ?

Which one of the below routines to use to destroy the PDF object :-

$doc->getValue($object)
For INTERNAL use Dereference a data object, return a value. Given an node object of any kind, returns raw scalar object: hashref, arrayref, string, number. This function follows all references, and descends into all objects.

$doc->getObjValue($objectnum)
For INTERNAL use Dereference a data object, and return a value. Behaves just like the getValue() function, but used when all you know is the object number.

$doc->dereference($objectnum)

$doc->dereference($name, $pagenum)
For INTERNAL use Dereference a data object, return a PDF object as a node. This function makes heavy use of the internal object cache. Most (if not all) object requests should go through this function. $name should look something like '/R12'.