How do I rewrite args with nginx if and only if a variable is set?

Question

I can't nest if and I don't have an and operator to use with if, so how would i un-nest this:

if ($AUTHENTICATED) {
    proxy_pass http://backend;
{
if (!$AUTHENTICATED) {
    if ($args ~ out=xml) {
        rewrite (.*)$ $1.xml break;
    }
    if ($args ~ out=csv) {
        rewrite (.*)$ $1.csv break;
    }
 }

Answer 1

if ($AUTHENTICATED) {
    proxy_pass http://backend;
    break;
}

if ($arg_out = xml) {
    rewrite ^ $uri.xml break;
}

if ($arg_out = csv) {
    rewrite ^ $uri.csv break;
}

but, please note: http://wiki.nginx.org/IfIsEvil