Probably something wrong in your code, I've tested following script: 
use strict;
use warnings;

use LWP::UserAgent;
use HTTP::Request::Common;
my $message;
my $userAgent =
  LWP::UserAgent->new( agent => 'Perlprogram/0.1', keep_alive => 1 );
$message = "UserID: Username, Password: password";
my $response = $userAgent->request(
    POST 'http://example.com/',
    Content_Type => 'application/text',
    Content      => $message
);

[download]
And here is the request I've got: 
POST / HTTP/1.1
TE: deflate,gzip;q=0.3
Keep-Alive: 300
Connection: Keep-Alive, TE
Host: example.com
User-Agent: Perlprogram/0.1
Content-Length: 36
Content-Type: application/text

UserID: Username, Password: password

[download]

In reply to Re^3: HTTP Post read response , Post again by zwon
in thread HTTP Post read response , Post again by perljunkie

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