I recall this exact problem (or close enough) was asked on ActiveState's ActivePerl mailing list recently. In general I remember seeing some things where the MS IE client has some MS-only way of communicating it's identity to the server but only if you do some Microsoft thing. It sounds like a neat idea but I'm not familiar enough to say exactly what that was. If no one here pulls up the answer I'd suggest asking over there. I think it might have required MS client and server and the perhaps IIS + ASP or something. There was probably also a hook into ActiveDirectory but... well I just don't remember. Either I'm conflating two threads or the final solution was not possible through perl.

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printf "You are here %08x\n", unpack "L!", unpack "P4", pack "L!", B::svref_2object(sub{})->OUTSIDE