PROCEDURE (ram$altml) alter_marked_lines, altml (
  alter_command, ac: string = $optional
  status)

  "$FORMAT=OFF
  VAR
    scr1: file = $fname($unique)
    scr2: file = $fname($unique)
  VAREND
  "$FORMAT=ON"

  IF NOT ($mfc = $mlc AND $mfl = $mll) THEN
    IF NOT $specified(ac) THEN
      ac = $screen_input('Enter alter command?')
    IFEND
    write_file f=scr1 l=m
    alter_file ac=ac i=scr1 o=scr2
    read_file f=scr2 il=$mfl p=b
    delete_lines l=m
    delete_file f=(scr1 scr2)
  IFEND

PROCEND alter_marked_lines
