use strict;   # Never-
use warnings; # -skip these.
use LWP::UserAgent;

my $urlRequest = "http://bamboohost/rest/api/latest/result/projectname-planname-latest/label";

my $xml = <<'';
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<label name="testlabel"/>

my $ua = LWP::UserAgent->new;
my $post = HTTP::Request->new( POST => $urlRequest );
$post->authorization_basic("username", "password");
$post->content($xml);
$post->content_type("application/xml");
print $post->as_string;

my $result = $ua->request( $post );