SOLVED: W00H00!

After much beverage goodness, and consideration, I ended up
answering my own question.  Since DBD::Oracle.pm doesnt want
to grab the nested_table as a type, convert the nested 
structure into a flattened table type ala table() and then 
pass it thru DBD::Oracle.  

So, if you replace the $sql line above with the following:

   my $sql = "select i.device_id, a.device_id from interfaces_objtab i, table(i.arp) a ";  

Instead of trying to figure out what a nested table is, 
it just returns a 'flattened' view of the data structure,
much to my delight, since DBD::Oracle can cope with that
a little better.

Thanks for the replies guys!