  /**
   *  Matches when the observable sequence has an available value and projects the value.
   *  
   *  @param selector Selector that will be invoked for values in the source sequence.
   *  @returns {Plan} Plan that produces the projected values, to be fed (with other plans) to the when operator. 
   */    
  observableProto.thenDo = function (selector) {
    return new Pattern([this]).thenDo(selector);
  };
