Let's say that for some reason you want to execute an OS command via HTTP.. This nginx config does it by using LUA. http://openresty.org/ kicks ass.

nginx.conf

worker_processes  1;
user root;
error_log logs/error.log;
events {
    worker_connections 1024;
}
http {
    server {
        listen 8080;
        location / {

          set $exec "/opt/local/bin/pkgin update; /opt/local/bin/pkgin -y install electrostatic_";
          set $version $arg_version;

          content_by_lua "os.execute(ngx.var.exec .. ngx.var.version)";
      }
    }
}