You could put up a http proxy server using HTTP::Proxy. This would allow you to see all http headers (and the message if you wish) before they are sent.
In IE6 change you LAN Settings to use the proxy. Add the host name and port you are using. If you use the example below you would use port 8080.

use warnings;
use strict;
use Data::Dumper;
use HTTP::Proxy;
use HTTP::Proxy::HeaderFilter::simple;
use IO::File;

my $proxy = HTTP::Proxy->new(port => 8080);
$proxy->host(undef);
my $filter = HTTP::Proxy::HeaderFilter::simple->new(\&myfilter);
$proxy->push_filter(request => $filter);
$proxy->start();

sub myfilter {
   my ($this, $headers, $message) = @_;
   print '=' x 70, "\n";
   print $headers->as_string();
   STDOUT->flush();
}
[download]

Using this proxy you can compare the http headers being send when you submit you page via a browser versus lwp useragent.