pull up shifted

def caesar_cipher(str, shift = 5)
  alpha = ('a'..'z').to_a
  shifted = []

  str = str.split('')
  str.each do |e|
    shifted << if e =~ /[A-Za-z]/
                 e == e.downcase ? alpha[alpha.index(e) - shift] : alpha[alpha.index(e)].upcase
               else
                 e
               end
  end

  shifted.join
end