use Stream qw/node drop list_to_stream/;

  my @tokens = (
    node( OP  => '+' ),
    node( VAR => 'x' ),
    node( VAL =>  3  )
  );
  my $stream = list_to_stream(@tokens);

  use Data::Dumper::Simple;
  while (my $node = drop($stream)) {
    print Dumper($node, $stream);
  }