var app = angular.module('plunker', []);

app.value('helloService', 'hello');

app.config(function($provide) {
  $provide.decorator('helloService', function($delegate, $log) {
    $log.info('decorated!!');
    return $delegate + ' world!';
  })
})


app.controller('MainCtrl', function($scope, helloService) {
  $scope.hello = helloService;
});
<!DOCTYPE html>
<html ng-app="plunker">

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="angular.js@1.2.x" src="https://code.angularjs.org/1.2.16/angular.js" data-semver="1.2.16"></script>
    <script src="app.js"></script>
  </head>

  <body ng-controller="MainCtrl">
    <p>{{hello}}</p>
  </body>

</html>
/* Put your css in here */