_arg_chk                     argument check

    TRUE/FALSE.  Default value = FALSE.  If FALSE, the NUMBER of  arguments
    passed to a user  defined function is checked  only to ensure that  the
    number is less than or equal to the number defined.  Arguments defined,
    but not passed are initialized  and passed for use as  local variables.
    If TRUE, the NUMBER of arguments  passed to a user defined function  is
    checked  against  the  number  defined.    If  the number passed is not
    exactly equal  to the  number defined,  an error  message is issued and
    execution halted.  For this  case, any local variables must  be defined
    with the 'local' keyword.