>>550
I had trouble getting nginx and kareha to play together nicely in the past too, but I managed to "fix" it a while ago after modifying kareha to use PSGI instead of CGI (https://github.com/marlencrabapple/kareha-psgi). Not sure if that was the reason it suddenly started working, but it just happened to make a difference on my end.

Just in case that wasn't the reason why it started working, try using a location directive like location ~ (admin|kareha|captcha).pl { ... } when passing stuff to fcgiwrap.