= Delete set of lines.

        DROp  {x | nx} [rep] {all | .lab1 .lab2}

          (DELete can be used on edit screen alternatively.)

            -x  :delete excluded lines at once.
             nx :delete not excludeed lines at once.

            -rep:replace deleted lines by one line " nn lines deleted ".
            -all:through the file
            -.lab1/2:Limit drop line range using a pair of label
                    on lineno column. line number may be used so as to
                    limit line range with no label on lineno column.
                 ex) "DRO x .from .to"  , "DRO x .120 .150".