{
    "version": "15320029",
    "global": {
        "ap": {
            "log": "info",
            "hyd": {
                "log": "info",
                "qo": false
            }
        },
        "cus": [
            {
                **"cp": "10000"**,
                "ser": "XYZ",
                "usesr": false,
                "services": {
                    "acc": {
                        "ips": {
                            "usesr": false
                        }
                    }
                },
                "q": {
                    "policy": "CAP",
                    **"custcap": 3000000**
                }
            },
            {
            "cp": "10441",
                "ser": "abc",
                "usesr": false,
                "services": {
                    "acc": {
                        "ips": {
                            "usesr": false
                        }
                    }
                },
                "q": {
                    "policy": "CAP",
                    "custcap": 3000000
                }
            }
         ]  
      }


##</code><code>##


#!/usr/bin/perl

use strict;
use warnings;
use JSON;

my $json;
{
   open my $fh, "<", "cfg.txt"
      or die("Can't open file \"/Users/hsivaram/cfg.txt\": $!\n");
   local $/;
   $json = <$fh>;
}

my $data = decode_json($json);

for my $cus (@{ $data->{global}{cus} }) {
   $cus->{q}{custcap} = 99999
      if $cus->{cp} == 10000;

}

$json = JSON->new->utf8->pretty->encode($data);

{
   open my $fh, ">" ,"cfg.txt"
      or die("Can't open file \"/Users/hsivaram/cfg.txt\": $!\n");
   local $/;

   print $fh $json;


}