Rubyでaliasを使った特異メソッドの上書き方法

stdout_hook_singleton_method.rb

#!ruby -Ku
# override_method/stdout_hook_singleton_method.rb
$KCODE = 'u'

# sample of override singleton method
require "kconv"

$stdout.sync = true

class << $stdout
  alias :old_write_for_sjis_filter :write
  def write(str)
    #old_write_for_sjis_filter str.to_s.kconv(Kconv::SJIS, Kconv::UTF8)
    #old_write_for_sjis_filter str.to_s.tosjis
    # change to sjis AS IS
    old_write_for_sjis_filter NKF.nkf('-sxm0', str.to_s)
  end
end
puts "表が怖い噂のソフト"
puts "UTF-8→SJISフックｷﾀ━（ﾟ∀ﾟ）━ !!"
puts "▶✉✦❤➡✖✔✸●■◢ ◣ ◤ ◥◧ ◨ ◩ ◪▲▼▶◀♂ ♀ ♪ ♫ ☼"
puts "テストまげもりまげもり"
puts "お前の脳天などこのテポドンキックで粉々に粉砕してやるわアアア～～～～～～！"

解説元サイト： Ruby/特異メソッドの上書きと退避 - TOBY SOFT wiki