       1mlvarpop 4m22mvar24m ?4mindexExpr24m? ?4mstring24m?
              The  1mlvarpop  22mcommand  pops (deletes) the element indexed by the
              expression 4mindexExpr24m from the list  contained  in  the  variable
              4mvar24m.   If  4mindex24m  is  omitted, then 0 is assumed.  If 4mstring24m, is
              specified, then the deleted element is replaced by  4mstring24m.  The
              replaced  or  deleted  element is returned.  Thus ``lvarpop argv
              0'' returns the first element of argv, setting argv  to  contain
              the remainder of the string.

              If the expression 4mindexExpr24m starts with the string 1mend22m, then 1mend0m
              is replaced with the index of the last element in the list.   If
              the  expression  starts  with 1mlen22m, then 1mlen 22mis replaced with the
              length of the list.
