I think I need to rephrase my question. Right now, my nginx.conf looks like this:

location ~*/path1/{
if (-f $document_root/error503.html) {
return 503;
}
}

error_page 503 <path_to_static_file>?arg1=$arg_queryparam1&arg2=<last path from url>

As you can see, if there is a 503 error, then I return a static file. The arguments to the static file are:
1. the param from url whose name is queryparam1,
2. the last path from the url

Now how do I fetch the last path from the url and pass it as a param to the static file? I'm new to Nginx, so I'm not sure if I'm doing this right.

Thanks.