I'm using a CoffeeScript dialect called LiveScript: http://livescript.net/ . A test case is below, executing it either in the interactive LiveScript interpreter or by saving it to test.ls and running with lsc test.ls causes it to hang after outputting "foo" and "bar" (so it's hanging on the shell.exec call).

console.log 'foo'
shell = require('shelljs')
console.log 'bar'
console.log shell.exec('ls')
console.log 'baz'

To test, save to test.ls and run with lsc test.ls.

Interestingly the code above works fine when pre-compiling the LiveScript to Javascript and executing with node, so it might actually be an issue with lsc: "lsc -c test.ls && node test.js" runs correctly.