MODIFY with REPLACE does rewrite the observation, but not with the value
of the changed hash variable. With put _all_ you can see that the
variable has been changed and the SAS log indicates "There were 1
observations rewritten", but the data set does not contain the changed
value.

The MODIFY statement only updates variables that will be modified in a
DATA step.  The MODIFY statement wasn't changed to recognize that
component methods such as the hash object could change variables.

A workaround is to place a dummy assignment somewhere in the DATA step:

  if 0 then CALL MISSING(data);

  -or-

  if 0 then data = data;

Note that you will need an explicit length declaration since it is a
character variable.

Operating System and Release Information