gistfile1.js

require.def({
  'increment': {
    'requires': ['math'],
    'factory': function() {
      var exports = arguments[0].exports,
          require = arguments[0].require,
          module = arguments[0].module;
      var add = require('math').add;
      exports.increment = function(val) {
          return add(val, 1);
      };
    }
  },
  
  'math': {
    'requires': [],
    'factory': function() {
      var exports = arguments[0].exports,
          require = arguments[0].require,
          module = arguments[0].module;
      var add = require('math').add;
      exports.add = function() {
          var sum = arguments[0];
          for (var i=1; i<arguments.length; i++) {
              sum += arguments[i];
          }
          return sum;
      };
    }
  }
});

require.async('increment', function(mod) {
  var inc = mod.increment;
  var a = 1;
  inc(a); // 2
});