Using an object/map/set instead of a switch statement.

reply.coffee

inputs = [
  "hello"
  "howdy"
  "how's it going?"
  "what's up?"
  "yo"
]

output = "Hey!"

# Doing this will make searching faster, especially if the code will be run
# more than just a few times.
inputSet = {}
inputSet[i] = true for i in inputs

# This function tests whether i is a member of `inputs` (and `inputSet`) above
# and if so, prints a message containing both the input and output.
reply = (i) ->
  if inputSet[i]
    console.log "#{i} => #{output}"

# process.argv is node's way of getting at the command line. This just runs
# reply on each item on the command line.
reply input.toLowerCase() for input in process.argv

# So running it looks like this:

# > coffee reply.coffee "Today?" "Yo" "Tomorrow?" "Howdy" "What's UP?"
# yo => Hey!
# howdy => Hey!
# what's up? => Hey!