gistfile1.js

macro module {
  case $body => {
    define(function (require, exports, module) {
      $body
    });
  }
}

module {
  var x = require('x');
  exports = function foo() {
    return 'foo' + x
  }
}

// outputs:

define(function (require$1, exports$2, module$3) {
    {
        var x$6 = require('x');
        exports = function foo() {
            return 'foo' + x$6;
        };
    }
});

Note, exports$2 does not match the reference to exports in the function body (line 21) - same with require$1 and require (line 20). It's fine to sanitize symbols, but you gotta be consistent in scope.