Update:I reread your post and noticed that you asked for a script. our very own davorg maintains a list of easy to use scripts at nms Perhaps something like Formmail is more up your alley.

Your question isn't too clear, but I'm going to take it that you want additional email headers, such as X-Mailer: or X-Referring-IP: headers.

Thunders has already given good pointers to the modules that you should look into if you decide to write this sort of thing yourself.

There are many scripts out there that can do this, although I would suggest you try and understand what the script is doing - some of the scripts out there are far from perfect.
The already mentioned nms should be considered one of the best.
If you're looking for a full-on webmail system, then look at acmemail or Neomail.

Here's a quick example of how to send an email with extra email headers I've russled up - it's pretty much what's in the documentation with some extra headers added. Note:

• I haven't tested it.
• There is no error checking
• I also think it looks horrid :-)

#!/usr/bin/perl -w

use strict;
use Net::SMTP;

my $smtp = Net::SMTP->new('mailhost.foo.com');

$smtp->data();
$smtp->datasend("To: user@bar.com\n");
$smtp->datasend("X-Mailer: Random dodgy email script\n");
$smtp->datasend("X-My-Favourite-Whisky: Glenfarclas\n");

# The following newline is the delimiter between the header
# and the body.
# For more info, on headers and how to form a email
# you should read the RFC for SMTP. 

$smtp->datasend("\n"); 

# Following line is the message body.

$smtp->datasend("If this works, you've got Perl to thank.\n");

$smtp->dataend();
$smtp->quit;
[download]

Update: Added a comment to the example code to clearly show the header and body sections of the transaction.