The most straight forward hello world example I could think of...

HelloWorld.rb

class Foo
  def self.foo(*args)
    args.each { |arg|
      print arg[arg.keys.first]
    }
    yield
  end
end

puts Foo.foo({:beep => "hello"},{:word=>" "}){x={:word => "world"};Foo.foo({:word => "there"},{:word => " "}){{:hello =>{:there=>{:world =>x[:word]}}}}}[:hello][:there][:world]

# Or, more simply

puts Foo.foo({
  :beep => "hello"
}, {
  :word => " "
}) {
  x = { 
    :word => "world"
  }
  Foo.foo({
    :word => "there"
  },{
    :word => " "
  }) {
    { 
      :hello => { :there => { :world => x[:word] } }
    }
  }
}[:hello][:there][:world]

"Ruby can be so easy on the eyes!"