-- accepts either 3 integers or a single property list
on foo (arg1, arg2, arg3)
  if ilk(arg1)=#propList then
    args = arg1
    arg1 = args[#arg1]
    arg2 = args[#arg2]
    arg3 = args[#arg3]
  end if
  put "arg1="&arg1
  put "arg2="&arg2
  put "arg3="&arg3
end

foo(1,2) -- 3rd argument omitted
-- "arg1=1"
-- "arg2=2"
-- "arg3="

foo([#arg3:3]) -- only 3rd argument specified
-- "arg1="
-- "arg2="
-- "arg3=3"