#!/usr/bin/perl

use warnings;
use strict;

my $fh;
# Reading one line from "test.json":
open($fh, "<", "test.json") or die;
my $JSON_DATA = <$fh>;
chomp($JSON_DATA);
close($fh);

my $WEBADDRESS;
my $ip = "5.5.5.5";
if ($JSON_DATA -ne "") {
    $WEBADDRESS="webaddress:jq.webaddress" . $JSON_DATA;
    $JSON_DATA =~ s/$WEBADDRESS/webaddress\:$ip/g;
    # Writing to "test.json":
    open($fh, ">", "test.json") or die;
    print $fh $JSON_DATA;
    close($fh);
}