nginx v0.7.64 on CentOS 5.3

We would like to be able to disable keepalive based on the User-Agent - specifically, we'd like to disable for MSIE 4.x,5.x,6.x

Even though the docs suggest it should work, the following config extract is rejected. We've tried various ways of setting the keepalive value - doesn't matter if we try keepalive_timeout or keepalive_requests - it won't let us change the value. Unfortunately we also can't do

[code]
keepalive_timeout $someVariable
[/code]

here's the extract

[code]

server {
listen 85;
server_name www.testingblah.com;

ancient_browser msie 4;
ancient_browser msie 5;
ancient_browser msie 6;

set $kvalue keepaliveon;
if ($ancient_browser){
set $kvalue keepaliveoff;
}

if ($kvalue = keepaliveon) {
keepalive_requests 50; //line 52
}
if ($kvalue = keepaliveoff) {
keepalive_requests 0;
}

location / {
proxy_pass http://WebHTTP;
}

}
[/code]

Error Message on startup is:

[emerg]: "keepalive_requests" directive is not allowed here in /data/apps/nginx/conf/nginx.conf:52

Any help - including alternative methods of achieving this requirement would be greatly appreciated.. we're looking for alternatives to lighttpd which is too buggy for us.

Update: using keepalive_requests is not going to work anyway as this would clearly be a per-socket one-time configuration - however, there should be a way of disabling keepalive for a specific request (based on User-Agent or any other factor) - setting the keepalive_timeout to 0 would seem reasonable?

Update: In apache we can also do this by downgrading a connection to HTTP/1.0 and/or setting nokeepalive=true