i am migrating from SQUID to NGINX.

While using SQUID, we had a IP based authentication layer:

if request to http://siteurl/servicename/service.php -> check list (data is saved in a file as tupel of ip:username:password)
if requesting client ip eq list ip -> rewrite url to backend as http://siteurl/servicename/service.php&username=username&password=password.


What is the best method to implement this on NGINX? I am pretty new to nginx, proxy function and ssl is working like a charm, but i dont know what method i should use.
At the moment i am experimenting to use the SimplePerl Module to handle my needs (i am also new to perl, but day to day there is a effort in handliung it). Is this the right way? Anyone there with a better idea?

Thanks in advance for your help - and thanks to Igor for this great piece of software!