use HTTP::Request::Common;
use LWP::UserAgent;
$ua = new LWP::UserAgent;
$ua->credentials('user', 'password');
my $req = new HTTP::Request::Common(POST $URL,  # note how it is called!
    [
        'txtUserID' => $USERID,
        'txtPassword' => $PASSWORD,
        'txtHeader' => $header,
        'txtReportArea' => $data,
        'onbtnSubmitReportWebEvent(btnSubmitReport)' => 'Submit Report'
    ]);
$req->authorization_basic('aas', 'mypassword');
print $req->status_line, "\n";