.Delete all lines contained a string.
      At first exclude lines containing the string by EXClude command,
      then use "DEL X ALL" or"DROp X ALL" command
      To delete all lines not include the string, use DEL/DROP NX ALL.
      To display all lines containing the string use FINd cmd
      after excluded all line by "x all" cmd.
      To select the line range around the line containing search word,
      use -a and/or -b option.
      use FLIp(or alias XX) cmd to exchange displayed and excluded lines.

      Regular expression or P'pic-str' format is supported to search string,
      and this is available for CHAnge cmd for replaced string search.