Any procedure or class source file can begin with one or more
USING statements, each of which identifies a fully qualified class or interface type name or the package name for one or more classes or interfaces that the file references. Each
USING statement specifies one or more classes or interfaces defined in a given package whose object type names you can reference using their unqualified class or interface names (without specifying the package). For more information, see
Referencing an object type name without its package.
