FAQ 4.46: How do I handle linked lists?

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4.46: How do I handle linked lists?

    In general, you usually don't need a linked list in Perl, since with
    regular arrays, you can push and pop or shift and unshift at either end,
    or you can use splice to add and/or remove arbitrary number of elements
    at arbitrary points. Both pop and shift are both O(1) operations on
    Perl's dynamic arrays. In the absence of shifts and pops, push in
    general needs to reallocate on the order every log(N) times, and unshift
    will need to copy pointers each time.

    If you really, really wanted, you could use structures as described in
    perldsc or perltoot and do just what the algorithm book tells you to do.
    For example, imagine a list node like this:

        $node = {
            VALUE => 42,
            LINK  => undef,

    You could walk the list this way:

        print "List: ";
        for ($node = $head;  $node; $node = $node->) {
            print $node->, " ";
        print "\n";

    You could add to the list this way:

        my ($head, $tail);
        $tail = append($head, 1);       # grow a new head
        for $value ( 2 .. 10 ) {
            $tail = append($tail, $value);

        sub append {
            my($list, $value) = @_;
            my $node = { VALUE => $value };
            if ($list) {
                $node-> = $list->;
                $list-> = $node;
            } else {
                $_[0] = $node;      # replace caller's version
            return $node;

    But again, Perl's built-in are virtually always good enough.


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