There are two issues here:

• changing the http-version: The only way to do this that I have found is to set an Environment Variable
• url-encoding: Just set the content with the content method provided by HTTP::Request

Here is a small example that should do what you wanted:

use strict;

sub BEGIN {
  # force HTTP version to 1.0
  $ENV{PERL_LWP_USE_HTTP_10} = "1";
}

use LWP::UserAgent;
use HTTP::Request::Common qw(POST);

my $ua = new LWP::UserAgent ();

my $req = POST 'http://localhost:4443/test.pl';

$req->content("<user>john\@doe</user>");
print $req->as_string;

my $response = $ua->request($req);
print $response->as_string;
[download]

Update:Please be careful when using the "trick" with the Environmant Vaiable, as I have seen it in the code not in any documentation. So I believe that this is an inofficial feature, which could disappear with a new version of LWP.
---- kurt