POKEPLUS axmud-object-property, expression

   Synopsis:
      Adds a number to the value of an Axmud internal scalar property

   Notes:
      POKE gives Axbasic scripts access to some of Axmud's internal data (see
         the help for the POKE statement for a full explanation).
      POKEPLUS is similar to POKE, but it only sets the value of scalar
         properties such as "world.current.longName". It cannot be used to set a
         list property such as "world.current.doorPatternList", a hash property
         such as "world.current.currencyHash" or a Perl object such as
         "world.current".
      POKEPLUS modifies the value of the scalar property by adding the value of
         the expression. Both values must be numeric.
      Much of Axmud's internal data is read-only, and cannot be modified with
         POKE or with this statement. If you try to modify a read-only property
         you will get an 'operation failure' error.

   Warning:
      Do not try to modify Axmud's internal data unless you know what you are
         doing. Read the Axmud manual before you try to POKE anything. (The
         examples below are safe, but backup your data first.)

   Examples:
      ! Increase the number of consecutive empty lines that are suppressed
      POKEPLUS "world.current.suppressEmptyLineCount", 2
