With a patched swig the output of poly.pl should be:

a is a Object/perl-object
b is a Derived/perl-derived
c is a Object/perl-object
d is a Derived/perl-derived

   The self() function returns an Object*, but swig knows how to
check the classname() function for the real C++ type.  classname()
must return a string that matches the C++ and Perl shadow class names.
A typemap for the Object* (the return type of self) must also be
provided in the interface file.
   With an unpatched swig or without the typemap from the interface file
the output would be:

a is a Object/perl-object
b is a Derived/perl-derived
c is a Object/perl-object
d is a Derived/perl-object

  Note the difference in the last line, perl has lost the type information
of the d pointer, and now thinks d is just an Object, not a Derived.
Polymorphic pointers like this can be useful when returning pointers to
related objects (neighbors, parents, children, ...) in a complex database.
The self() pointer was just to simplify the example.

   Unless a typemap overrides the return type of a function (as in this
example) the code should function as before, as no type-modifying typemaps
were possible before this patch.

-Drake Diedrich (Drake.Diedrich@anu.edu.au)