I think the key is to understand how ActiveX fits into the rest of the Microsoft architecture. AFAIK, ActiveX is build on the COM infrustructure. In fact, ActiveX controls are simply COM objects that implement automation (the IDispatch interface).

So really, the question is whether Perl can communicate with a COM object via the well-defined ActiveX interfaces. Using PerlCtrl (formerly PerlCOM), part of ActiveState's Perl Dev Kit, this is possible and many examples exist.