use LWP::UserAgent;
my $urlRequest = "http://bamboohost/rest/api/latest/result/projectname-planname-latest/label";
my $message = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?><label name=\"testlabel\"/>";
my $ua = LWP::UserAgent->new;
my $req = HTTP::Request->new( POST => "$urlRequest");
$req->authorization_basic("username", "password");
$req->content($message);
$req->content_type('application/xml');
my $result = $ua->request( $req );