code: def extract_words(wildcard = Word::WILDCARD)
        word = /".*?"|'.*?'|#{wildcard}?\w+#{wildcard}?/ # "word1 word2" | 'word1 word2' | word
        scan(word).flatten.map{|x| x.gsub(/"|'/, '"')}.uniq
      end
docs: "a b 'c d'" => ["a", "b", "\"c d\""]