# File lib/multiruby.rb, line 138
  def self.extract_latest_version url, matching=nil
    file = URI.parse(url).read
    versions = file.scan(/href="(ruby.*tar.gz)"/).flatten.reject { |s|
      s =~ /preview/
    }.sort_by { |s|
      s.split(/\D+/).map { |i| i.to_i }
    }.flatten
    versions = versions.grep(/#{Regexp.escape(matching)}/) if matching
    versions.last
  end