Greetings Gracious Monks of the Monastery!

I'm working on a simple newsletter script that receives email addresses from a form and stores them in a file. Here is what I have so far:

#!/usr/bin/perl -wT

use strict;

use CGI;
use Email::Valid;


# retrieve form parameter(s)
my $q = new CGI;

my $tainted_email = $q->param("email");

# check that $tainted_email is valid
my $is_valid = Email::Valid->address('$tainted_email');

# if $tainted_email is valid, store the address in $email
my $email = "";

if ($is_valid) {
    $email = $tainted_email;
}

# grab user information
my $ip_address = $ENV{REMOTE_ADDR};
my $referrer   = $ENV{HTTP_REFERER};


if ($email) {
    # store the data in a plain text file
    open LOG, ">>newsletter.txt" or die "Cannot Access Logfile: $!"
    print LOG "$email : $ip_address : $referrer\n";
    close LOG;
}


# print thank-you page

[download]

The checks based on whether or not $tainted_email is valid seem rather messy to me. My primary concern is validating all the parameters that aren't sent to the script, including the IP address and the referrer. I want to ensure they're of valid structure, and of valid length. I'm also looking for a simple-as-possible storage mechanism for them (escaping issues?).

Also - I don't have access to httpd.conf but I'd like to ensure no one can read the files the info is stored in. Is there a simple way to do this (ie file permissions? I'm not sure what user the webserver is running as), or do I have to have .htaccess files enabled? Thank you for your time :)

In reply to Subscription form script by Anonymous Monk

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