old_contents: 'use strict';
  
  var config = require('../config');
  var gulp   = require('gulp');
  var del    = require('del');
  
  gulp.task('clean', function() {
  
    del([config.dist.root]);
  
  });
new_contents: 'use strict';
  
  var config = require('../config');
  var gulp   = require('gulp');
  var del    = require('del');
  
  gulp.task('clean', function(cb) {
  
    del([config.dist.root], cb);
  
  });
  
subject: Make tasks running in sequence