clarify variables available inside the .js files in README.md

README.md

@@ -285,6 +285,23 @@ Dynamic values of headers can be filled with valid JS statements such as:
 X-Subject-Token: #header ${require('uuid/v4')()};
 ```
 
+Because of how the javascript files are evaluated, you can also access the following variables inside the .js file:
+* `request`
+* `context`
+* `value`
+
+Relative `require()` import statements for relative files will not work out-of-the-box, but since `context` contains the path to the directory where your .js file is, you can do the following hack to get them to work.
+
+```js
+/* globals request, context, path */
+
+// actually path is already available via the eval'd scope
+// var path = require('path');
+var fooFunc = require(path.join(context, 'foo.js'));
+
+module.exports = fooFunc(request).bar;
+```
+
 ## Custom response status
 
 You can specify response status (200, 201, 404. etc.) depending on request parameters. To do this, you need to use `#import './code.js';` in first line of your mock file: