longest palindrome finder

palindromes.rb

def find_longest_palindrome(string)
  (string.length/2).downto(1) do |i|
    backrefs = "\\#{(-i..-1).map(&:abs).join("\\").sub(i.to_s, "#{i}?")}"
    string.scan(/#{'(.)'*i}(#{backrefs})/).tap do |a|
      return a.take(i).join unless a.empty?
    end
  end
end