my @items = (1,5,6,3,5,2,4);
my $index = 0;

sub do_next
{
  do_something($items[$index]);
  $index = ($index+1) % @items;
}

##</code><code>##

my @items = (1,5,6,3,5,2,4);
my $index = -1;

sub add_item
{
  push @items, @_;
}

sub do_next
{
  if (@items)
  {
    $index = ($index+1) % @items;
    do_something($items[$index]);
  }
  else
  {
    $index = -1;
  }
}

##</code><code>##

sub remove_item
{
  my %del = map {$_=>1} @_;

  my @part_1 =
    grep { !exists $del{$_} } @items[0..$index];
  my @part_2 =
    grep { !exists $del{$_} } @items[$index+1..$#items];

  $index = $#part_1;
  @items = (@part_1, @part_2);
}