#!/usr/bin/env perl

my @arr=();
my $head=['head', undef];
push @arr, $head;

foreach (a .. g){
 push @arr, [$_, undef];
}

my $cur=$head;
foreach (0 .. @arr){
 $arr[$_]->[1] = $arr[$_+1];
}

$cur = $head;

while ($cur->[1]){
 print "$cur->[0] ";
 $cur = $cur->[1];
}
print "$cur->[0] \n"; #last one

my %hash=(); # ('nodeN', ref2ME)

my $n=1;
foreach (a .. g){
 $hash{node.$n} = [$_, undef]; # (node1, nextNode)
 n++;
}

my $N = scalar %hash;

# link them
foreach my $i (1 .. $N) {
    $hash{"node$i"}->[1] =
        ($i < $N) ? "node" . ($i + 1) : undef;
}

my $cur = "node1";

while (defined $cur) {
    my ($val, $next) = @{$hash{$cur}};
    print "$cur => $val -> ", (defined $next ? $next : "NULL"), "\n";
    $cur = $next;
}