function is_mri {

if ruby -e "exit(RUBY_ENGINE == 'ruby')"; then
  # RUBY_ENGINE only returns 'ruby' on MRI.
  return 0
else
  return 1
fi

}

function is_ruby_31_plus {

if ruby -e "exit(RUBY_VERSION.to_f >= 3.1)"; then
  return 0
else
  return 1
fi

}