sub authenticate {

    # Create a request
    my $req =
      HTTP::Request->new(
        POST => 'https://identity.api.rackspacecloud.com/v2.0/tokens' );
    $req->content_type('application/json');
    #my $json = '{"auth":{"RAX-KSKEY:apiKeyCredentials":{"username":"foo", "apiKey":"00000000000000000000000000000000"}}}';
    my $json = quotemeta( {"auth":{"RAX-KSKEY:apiKeyCredentials":{"username":$USERNAME, "apiKey":$API_KEY}}} );
    $req->content( $json );

    # Pass request to the user agent and get a response back
    my $res = $ua->request($req);

    # Check the outcome of the response
    if ( $res->is_success ) {
        # Do stuff ...
    } else {
        print $res->status_line, "\n";
    }

}