def beautify_name(first_name, last_name)
  full_name = "#{first_name.capitalize} #{last_name.upcase}"
  yield(full_name)
end

message = beautify_name("john", "lennon") do |full_name|
  "Greetings #{full_name}, you look quite fine today!"
end

puts message # => "Greetings John LENNON, you look quite fine today!"