「な〜ほ」に「ぬ」が含まれるか、みたいなのを判定する

nu.rb

#!/usr/bin/env ruby

your_class = 'ぬ'
hiragana = 'あいうえお' \
           'かきくけこ' \
           'さしすせそ' \
           'たちつてと' \
           'なにぬねの' \
           'はひふへほ' \
           'まみむめも' \
           'やゆよ'     \
           'らりるれろ' \
           'わをん'

if ARGV.length < 1 then
  print "argument required\n"
  exit
end

is_included = false

if ARGV[0].length == 1 then
  is_included = (ARGV[0] == your_class)
else 
  start = ARGV[0][0]
  finish = ARGV[0][1]

  selected = hiragana[hiragana.index(start) .. hiragana.index(finish)]

  is_included = selected.include?(your_class)
end

print (is_included ? 'included' : '') + "\n"