Error in code example

There is an error in the last code example:

``` javascript
var browserify = require('browserify')
  , envify = require('envify/custom')
  , fs = require('fs')

var bundle = browserify('main.js')
  , output = fs.createWriteStream('bundle.js')

b.transform(envify({
  NODE_ENV: 'development'
}))
b.bundle().pipe(output)
```
You should use **b** insead of **bundle** variable.