sub foo($x, $y, $z) {...}    # expects three scalars
    @onetothree = 1..3;          # array stores three scalars

    foo(1,2,3);                  # okay:  three args found
    foo(@onetothree);            # error: only one arg
    foo(*@onetothree);           # okay:  @onetothree flattened to three args