def captures?(fast = @fast)
      case fast
      when Capture then true
      when Array then fast.any?(&method(:captures?))
      when Find then captures?(fast.token)
      end
    end
def captures?(fast = @fast)
      case fast
      when Capture then true
      when Array then fast.any?(&method(:captures?))
      when Find then captures?(fast.token)
      end
    end
Look recursively into @param fast to check if the expression is have
 captures.
 @return [true] if any sub expression have captures.