Tutorial

Good tutorials on writing user scripts for operator are available at http://www.kaply.com/weblog/operator-user-scripts/

The only difference with a poshZone script is how you define the semantic scope:
If content is markep up as below:

<div class="poshZone">
    <span class="poshZoneDescription">Movie: Cold Mountain</span>
    <div class="movie">
        <span class="movieName">Cold Mountain</span>. 
    Made in <span class="movieYear">2003</span>. Watch it.
        <p>In the waning days of the American Civil War, a wounded soldier (Law) 
    embarks on a perilous journey back home to Cold Mountain, North Carolina 
    to reunite with his sweetheart (Kidman). Based on the novel by Charles Frazier.
        </p>
    </div>
</div>

then a user script that is interested in movie nodes that have a movie name should have a sematic scope specification as follows:

var rentalq = {
    description: "Add to RentalQ on myjavaserver.com",
    shortDescription: "RentalQ",
    scope: {
        semantic: {
        "poshZone" : {
            custom: "['movie']['movieName']"
        }
    }
}

The user script action handler can then retrieve the inforamation as below:

var poshContent = Microformats.poshZone.mapPoshZone(semanticObject.resolvedNode);
var body = "subscriberId=user123&password=password&movieName=" + 
            poshContent['movie']['movieName'] + 
            "&movieYear=" + 
            poshContent["movie"]['movieYear'];

Finally here is the complete action handler script that does a POST. Note that support for authentication is yet to come. For now, could choose to prompt the user for credentials.

doAction: function(semanticObject, semanticObjectType, propertyIndex, event) {
    //from http://www.kaply.com/weblog/wp-content/uploads/2007/10/fpu.js

    if (semanticObjectType == "poshZone") {
      var poshContent = Microformats.poshZone.mapPoshZone(semanticObject.resolvedNode);
            var body = "subscriberId=user123&password=password&movieName=" + 
            poshContent['movie']['movieName'] + "&movieYear=" + poshContent["movie"]['movieYear'];
          var ios = Components.classes["@mozilla.org/network/io-service;1"].
                getService(Components.interfaces.nsIIOService);
          var referrerURI = ios.newURI("http://www.myjavaserver.com/servlet/bagheera.movierentals.RentalQHomePage", null, null);
          var stringStream =  Components.classes["@mozilla.org/io/string-input-stream;1"].
                        createInstance(Components.interfaces.nsIStringInputStream);
            if ("data" in stringStream) // Gecko 1.9 or newer
            stringStream.data = body;
            else // 1.8 or older
            stringStream.setData(body, body.length);

      var postData = Components.classes["@mozilla.org/network/mime-input-stream;1"].
                    createInstance(Components.interfaces.nsIMIMEInputStream);
      postData.addHeader("Content-Type", "application/x-www-form-urlencoded");
          postData.addContentLength = true;
          postData.setData(stringStream);

          if (event) {
              var rentalQurl = "http://www.myjavaserver.com/servlet/bagheera.movierentals.RentalQ";
              openUILink(rentalQurl, event, undefined, undefined, undefined, postData, referrerURI);
            } else {
            getBrowser().webNavigation.loadURI(
            "http://www.myjavaserver.com/servlet/bagheera.movierentals.RentalQ", 0, referrerURI, postData, null);
             return true;
          }
    }
  }
};