The LIST attribute can be applied to a  formal  parameter  of  a
  routine  and  indicates  that  the  routine  can  be called with
  multiple actual parameters that correspond to  the  last  formal
  parameter named in the routine heading.

  You  can  also  use  the   ARGUMENT   and   ARGUMENT_LIST_LENGTH
  predeclared  routines when writing procedures and functions that
  use the LIST attribute.

  See the "HP Pascal Language Reference Manual" for  the  complete
  description of using the LIST attribute.