How to run two grunt watch tasks simultaneously

I’ve found using grunt-concurrent works:

concurrent: {
  options: {
    logConcurrentOutput: true
  },
  prod: {
    tasks: ["watch:A", "watch:C"]
  },
  dev: {
    tasks: ["watch:B", "watch:C"]
  }
}

Then:

grunt.registerTask("prod", ["concurrent:prod"]);
grunt.registerTask("dev", ["concurrent:dev"]);