Convert a hex string into a semipronouncable string of characters

hex_to_words.rb

#!/usr/bin/ruby

string = ARGV[0]
puts string.downcase.split("").map{|e|
  case e
  when "0"
    "ka"
  when "1"
    "tsu"
  when "2"
    "shi"
  when "3"
    "ha"
  when "4"
    "ko"
  when "5"
    "ma"
  when "6"
    "ku"
  when "7"
    "su"
  when "8"
    "so"
  when "9"
    "mu"
  when "a"
    "mo"
  when "b"
    "ya"
  when "c"
    "yu"
  when "d"
    "ki"
  when "e"
    "fu"
  when "f"
    "ni"
  else
    "INVAL"
  end
}.each_slice(2).to_a.map{|e| e.join}.join(" ")