a($_) while <DATA>;

for (sort keys %h){
	print "$_: my address is $h{$_}\n";
	print "last:  $h{$_}{'a'} >>> $h{$_}{'a'}{'c'}\n";
	print "next:  $h{$_}{'b'} >>> $h{$_}{'b'}{'c'}\n\n";
}

sub a {
		chomp;
		$t = shift;
		$h{$t}{'a'} = $l;
		$h{$t}{'c'} = $t;
		$$l{'b'} = $h{$t};
		$l = $h{$t};
}

__DATA__
a
b
c
d
e