[MRI only] Hello World in Ruby – the wrong way (Ruby Fiddle study with a brief touch on MRI C API)

hello, world.rb

# frozen_string_literal: true
require 'fiddle'
include Fiddle

GREETINGS = 'hello, world'

Handle.new.then do |lib|
  Function.new(
    lib['rb_eval_string'],
    [TYPE_CONST_STRING],
    TYPE_UINTPTR_T, # VALUE
    need_gvl: true
  ).call("$><<'#{GREETINGS}'+?\\n")
ensure
  lib.close
end