If the Win32 machines filesystem is visible to the unix box (via Samba or similar) then you could have the Win32 app create a Named pipe and the unix app can just open/read/write to/from that.

The nice things about this is that if the Win32 app creates the NP at a domain server, it can do so from any machine that can see the domain server and the unix app can run on any machine that can see that domain server. This indirection through a 3rd machine is rather easier to coordinate than ip.port combos.

Win32::Pipe allows (limited) access to the native Named Pipe apis from perl. The downside is that the implementation is a blocking API with no apparent mechanism for timeouts.