The global_replace procedure can be used for many
  filtering tasks. However any DECTPU commands can be
  used to build filters. The file being filtered is read
  into the buffer "filter_buffer" before the user filters
  are applied and written out afterwards.

  The following filter uses the DECTPU EDIT procedure to
  convert all characters to upper case:

     EDIT( filter_buffer, UPPER, OFF)

  Note that while a similar effect is possible using the
  COMPARE/IGNORE=CASE command, the filter can be applied
  to individual tests, whereas the IGNORE qualifier
  applies only to collections.

  The following filter searches for numbers and replaces
  them only if they are in a specified range:

     POSITION (BEGINNING_OF (filter_buffer));
     LOOP
         found_range := SEARCH_QUIETLY (number, FORWARD);
         EXITIF found_range = 0;
         POSITION (END_OF(found_range));
         MOVE_HORIZONTAL(1);
         value := INT(STR(found_range));
         IF (value>350) AND (value<570)
         THEN
             COPY_TEXT ("XXX");
             ERASE (found_range);
         ENDIF;
     ENDLOOP;

  The initial POSITION is required to ensure that the
  whole of the filter_buffer is processed, because the
  editing point is undefined at the start of each filter.
  Then, as each number is processed, the editing point is
  moved to the end of the number. The MOVE_HORIZONTAL
  procedure call is necessary because the previous
  POSITION leaves the editing point at the last character
  of the number, which would result in an immediate match
  on the next call to SEARCH_QUIETLY.