code: function VError(options)
  {
  	var args, causedBy, ctor, tailmsg;
  
  	if (options instanceof Error || typeof (options) === 'object') {
  		args = Array.prototype.slice.call(arguments, 1);
  	} else {
  		args = Array.prototype.slice.call(arguments, 0);
  		options = undefined;
  	}
  
  	tailmsg = args.length > 0 ?
  	    mod_extsprintf.sprintf.apply(null, args) : '';
  	this.jse_shortmsg = tailmsg;
  	this.jse_summary = tailmsg;
  
  	if (options) {
  		causedBy = options.cause;
  
  		if (!causedBy || !(options.cause instanceof Error))
  			causedBy = options;
  
  		if (causedBy && (causedBy instanceof Error)) {
  			this.jse_cause = causedBy;
  			this.jse_summary += ': ' + causedBy.message;
  		}
  	}
  
  	this.message = this.jse_summary;
  	Error.call(this, this.jse_summary);
  
  	if (Error.captureStackTrace) {
  		ctor = options ? options.constructorOpt : undefined;
  		ctor = ctor || arguments.callee;
  		Error.captureStackTrace(this, ctor);
  	}
  }
docs: /*
  Like JavaScript's built-in Error class, but supports a "cause" argument and a
  printf-style message.  The cause argument can be null.