so that you can write CoffeeScript instead of JavaScript in the Mongo Shell.
To use, just npm install -g cofmon and then use cofmon as you would the Mongo command.
In additon to being able to write CoffeeScript instead of JavaScript, any 24 character hex string that's wrapped in single quotes is automatically made into an ObjectId, i.e.
'51bb660191888d7acc355ed8' compiles to ObjectId('51bb660191888d7acc355ed8')
"51bb660191888d7acc355ed8" compiles to "51bb660191888d7acc355ed8"
Note that the quotes were reversed in a previous version. It was changed because the mongo repl returns object ids with double quotes, which meant you couldnt copy/paste the entire ID.