> AFAIK, the '$donot_cache ' you set here
> will not contain anything outside the if block.

You are right, I forgot to put "set $donot_cache = 0;" right before the if block, but it doesn't seem to be the problem.

Everything is fine regarding the availability of those variables, and I verified it by adding them as an HTTP header to all responses.

> In your case, why not just use 'fastcgi_no_cache
> $cookie_COOKIE-1$cookie_COOKIE-2$cookie_COOKIE-3'
> and skip the whole 'if' test?

Because those cookie names change -- they have random numbers appended to them, so I need to do a regex check for their prefixes.

I'll be sure to post an update if I find something.