anchor.diff:    REAL, INTENT(IN)                         :: rperturb
   
     CALL fs_read_field(serializer, savepoint, fieldname, field)
  -  CALL fld_perturb(field, rperturb)
  +  CALL ser_fld_perturb(field, rperturb)
   END SUBROUTINE fs_read_and_perturb_double_2d
   
   SUBROUTINE fs_read_and_perturb_double_3d(serializer, savepoint, fieldname, field, rperturb)
  
positive.code:   REAL, INTENT(IN)                         :: rperturb
  
    CALL fs_read_field(serializer, savepoint, fieldname, field)
    CALL fld_perturb(field, rperturb)
  END SUBROUTINE fs_read_and_perturb_float_3d
  
  SUBROUTINE fs_read_and_perturb_float_4d(serializer, savepoint, fieldname, field, rperturb)
  
negative.code:   REAL, INTENT(IN)                         :: rperturb
  
    CALL fs_read_field(serializer, savepoint, fieldname, field)
    CALL ser_fld_perturb(field, rperturb)
  END SUBROUTINE fs_read_and_perturb_float_4d
  
  SUBROUTINE fs_read_and_perturb_double_0d(serializer, savepoint, fieldname, field, rperturb)
  