#!/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;


}