PEEKSHIFT variable-name = axmud-object-property
PEEKSHIFT ARRAY variable-name = axmud-object-property

   Synopsis:
      Removes a value from the beginning of an Axmud internal list property

   Notes:
      PEEK gives Axbasic scripts access to most of Axmud's internal data (see 
         the help for the PEEK statement for a full explanation).
      PEEKSHIFT can only be used with list properties such as 
         "world.current.doorPatternList". It cannot be used with a scalar 
         property such as "world.current.name", a hash property such as 
         "world.current.currencyHash" or a Perl object such as "world.current".
      'variable-name' is set to the first value of the list property. In 
         addition, that value is removed from the list property. (PEEKSHIFT and 
         PEEKPOP are the only PEEK... statements that modify an Axmud internal 
         property.) If the list property is empty, a string variable is set to 
         "<<undef>>" and a numeric variable is set to 0.
      Much of Axmud's internal data is read-only, and cannot be modified 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 PEEKSHIFT anything. (The
         examples below are safe, but backup your data first.)

   Examples:
      ! Remove the first value from a list property and store it in an Axbasic
      ! global scalar variable
      PEEKSHIFT pattern$ = "world.current.doorPatternList"

      ! Remove the first value from a list property and store it in an Axbasic 
      ! global array
      PEEKSHIFT ARRAY patterns$ = "world.current.doorPatternList"
 
      ! Remove the first value from a list property and store it in an Axbasic 
      ! local scalar variable
      LOCAL pattern$
      PEEKSHIFT pattern$ = "world.current.doorPatternList"
