Again, I humbly approach the monastery ...

In a wizard-style web application I've created, I use the following data structure to track navigation:

$navigation_map = {
    first_page       => {
        PREVIOUS => '',
        NEXT     => 'second_page',
    },
    second_page      => {
        PREVIOUS => 'first_page',
        NEXT     => 'third_page',
    },
     third_page         => {
        PREVIOUS => 'second_page',
        NEXT     => 'fourth_page',
    },
    fourth_page         => {
        PREVIOUS => 'third_page',
        NEXT     => '',
    },
};
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which allows me to say $navigation_map->{second_page}{NEXT} to find out what the next screen should be.

Unfortunately, the same list of pages does not appear in each of the installations of this app, so constructing the navigation map and editing the links for each instance is a pain. What I should be able to do is use an array, so I can just do this:

$navigation_map = [qw(first_page second_page third_page fourth_page)];
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So I created an object to build the hash structure for me (from an array):

package List::Navigator;

sub new
{
    my $class = shift;
    my ($list) = @_;

    my $data = {};
    my ($previous, $next);
    for my $item (@$list)
    {
        $data->{$item}{PREVIOUS} = $previous;
        $data->{$previous}{NEXT} = $item if defined $previous;
        $previous = $item;
    }
    bless $data, $class;
}
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my $nav_list = [qw( first_page second_page third_page fourth_page )];

my $navigation_map = List::Navigator->new( $nav_list );
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