Zeus suprisingly enough supports ISAPI, but I don't know if it can deal with the ActiveState ISAPI filter. It does support FastCGI out of the box which should give you functionality similar to Apache::Registry.
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Coyote
Comment on (Coyote) Re: Re: ISAPI module for Zeus web server?`
Zeus webserver kicks serious butt. To be honest I am biased as I used to work for them!
Seriously though, I'm wondering why you would want to use Perl for ISAPI as you shouldn't gain an enormous advantage over Perl and FastCGI with Zeus as it is quite a hell of a lot faster than any other webserver and Perl is not a terribly fast language despite it's many other benefits.
If you want me to get you an answer from people who really know their onions, /msg me and 'll ask a friend there.