attribute_match (HTML::Selector)

    # File lib/action_controller/vendor/html-scanner/html/selector.rb, line 687
        def attribute_match(equality, value)
          regexp = value.is_a?(Regexp) ? value : Regexp.escape(value.to_s)
          case equality
            when "=" then
              # Match the attribute value in full
              Regexp.new("^#{regexp}$")
            when "~=" then
              # Match a space-separated word within the attribute value
              Regexp.new("(^|\s)#{regexp}($|\s)")
            when "^="
              # Match the beginning of the attribute value
              Regexp.new("^#{regexp}")
            when "$="
              # Match the end of the attribute value
              Regexp.new("#{regexp}$")
            when "*="
              # Match substring of the attribute value
              regexp.is_a?(Regexp) ? regexp : Regexp.new(regexp)
            when "|=" then
              # Match the first space-separated item of the attribute value
              Regexp.new("^#{regexp}($|\s)")
            else
              raise InvalidSelectorError, "Invalid operation/value" unless value.empty?
              # Match all attributes values (existence check)
              //
          end
        end