docs: function WHILE(condTask, runTask) {
      var runTasks = Array.prototype.slice.call(arguments, 1);
      runTasks.push(nextTask);
      runTask = waterfall(runTasks);
      var whileTask = IF(condTask, runTask);
      return whileTask;
  
      function nextTask(value) {
        return whileTask.call(this, value);
      }
    }