#!/usr/bin/env perl

use strict;
use warnings;

my @posts = qw{a b c d};
my %fence = (
    $posts[0],
    (map { $_ => $_ } @posts[1..$#posts-1]),
    $posts[-1]
);

print "$_ to $fence{$_}\n" for @posts[0..$#posts-1];

my @extra = qw{w x y z};
my %info;
$info{$posts[$_]}{extra} = $extra[$_] for 0..$#posts;

print "$_~$info{$_}{extra}\n" for @posts;

##</code><code>##

a to b
b to c
c to d
a~w
b~x
c~y
d~z