What is PL/XML?

PL/XML is a scripting language, implemented in XML, that can be passed into a PL/SQL procedure. The script can execute stored procedures, it has looping logic, conditional (CASE) logic, user defined variables, etc.

Where can I read more about PL/XML?

http://database-geek.com/2006/09/12/plxml-xml-based-scripting-for-plsql/