Execute Grunt tasks iteratively based on external config. It will allow you to modify the input parameters for the same tasks without modifying the Gruntfile.

distro.es.json

{
  "description": "Distribution for Spain",
  "distros": [
    {
      "id": "dev",
      "title": "Development Version",
      "endpoint": "http://localhost:3000/"
    },
    {
      "id": "qa",
      "title": "QA Version",
      "endpoint": "http://qa.hi.inet/"
    },
    {
      "id": "prod",
      "title": "Production Version",
      "endpoint": "http://movistar.es/"
    }
  ]
}

Gruntfile.js

grunt.initConfig(
  //The build task is in charge of creating a compilation enforcing  
  //one parameter in the HTML code: the url
  build: {
    //The default options for the build task
    options: {
      //The source file
      src: 'app/index.html'
    }
    /*
     * We will create here configurations dinamycally, 
     * one for each distribution in the external config distro file
     * we will generate:
    dev: {
      url: 'http://localhost:3000/'
      dest: 'dist/dev/index.html'
    },
    qa: {
      url: 'http://qa.hi.inet/',
      dest: 'dist/qa/index.html'
    },
    prod: {
      url: 'http://movistar.es/',
      dest: 'dist/prod/index.html'
    }
     */
  }
);

/**
 * Schedules a Grunt task to be run for a distro determined by 
 * the distro.js configuration file
 * @param {String} task the task name to execute
 * @cb {Function} cb Callback that returns a grunt
 *   configuration for that task
 */
function schedule(task, cb) {
  //Get the config for task ('build' in the example)
  var config = grunt.config.get(task),
  //Get the stored config for the distro (the distro.js file)
      distros = grunt.config('distro').distro;

  distros
      .map(cb)
      .forEach(function(configItem, index) {
        var distroId = distros[index].id;
        //Set the config for build:[dev, qa, prod]
        config[distroId] = configItem;
        //Schedule task to be run. build:[dev, qa, prod]
        grunt.task.run([task + ':' + distroId]);
      });
  //Store the config for 'build';
  //It has now the config for build:[dev, qa, prod]
  grunt.config.set(task, config);
}

grunt.registerTask('distros:build','Generate the distributions', function() {
  
  //DO the MAGIC here: We schedule a task, (build)
  //But we set the config for the specific distro in the 
  //iterator function
  schedule('build', function iterator(distro) {
    //We generate the configuration for the build task and this distro
    return {
      url: distro.endpoint,
      dest: 'dist/' + distro.id + '/index.html'
    }  
  });
  
  //Here we have configured the build task with three new subtasks (dev, qa, prod)
  //And we have scheduled its running.
});


grunt.registerTask('readDistributionFile', 'reads and configures Grunt for several distributions', function() {

  var distroFile = grunt.option('distro') ?
      'build/config/samples/distro.' + grunt.option('distro') + '.json' :
      'build/config/distro.json';

  var distro = grunt.file.readJSON(distroFile);

  grunt.config.set('distro', distro);
});

grunt.registerTask('build','Generate the distributions', [
    'readDistributionFile',
    'distros:build'
]);

shell

# Generate the software for dev, qa & production for Spain
grunt build --distro=es

# Generate the software dev, qa & production for Brazil
grunt build --distro=br