The documentation says:

The GetActiveObject() class method returns an OLE reference to a running instance of the specified OLE automation server. It returns undef if the server is not currently active. It will croak if the class is not even registered. The optional DESTRUCTOR method takes either a method name or a code reference. It is executed when the last reference to this object goes away. It is generally considered impolite to stop applications that you did not start yourself.

So you have to activate your server, usually by *win32 ole automation server programming details here*