taskHandler.js

// How to expose a global handler for my requestHandler to reach?
module.exports = handler = [];

exports.addToHandler = function(key, newFunction) {
	handler[key] = newFunction;
}

// To handle things from my requestHandler, I'm thinking:
var handler = require('./taskHandler');

handler.addToHandler('processMail', function() {
	// magic happens here...
});

handler[requestKey, params]();