Load node.js module from string in memory

How would I require() a file if I had the file's contents as a string in memory, without writing it out to disk? Here's an example:

// Load the file as a string
var strFileContents = fs.readFileSync( "./myUnalteredModule.js", 'utf8' );

// Do some stuff to the files contents
strFileContents[532] = '6';

// Load it as a node module (how would I do this?)
var loadedModule = require( doMagic(strFileContents) );