use Carp;

sub dive {
	my ($ref,@path) = @_;
	for my $i (0..$#path) {
		$ref = $path[$i]=~/^\[(\d+)\]$/
			? $ref->[$1] : $ref->{$path[$i]};
		if (!defined $ref) {
			carp "undef at: ".join('',
				map {/^\[\d+\]$/?$_:"{$_}"} @path[0..$i]);
			return undef;
		}
	}
	return $ref;
}

my $data = { this => { is => { a =>
		{ deep => { structure => [ 'abc', 'def', undef ]
	} } } } };

printf "<%s>\n", dive($data, qw/ this is a deep structure [0] /);
printf "<%s>\n", dive($data, qw/ this is a deep structure [3] /);
printf "<%s>\n", dive($data, qw/ this is an example /);

__END__

<abc>
undef at: {this}{is}{a}{deep}{structure}[3] at - line 10.
	main::dive(HASH(0x9e47a4), "this", "is", "a", "deep", "structure", "[3]") called at - line 22
Use of uninitialized value in printf at - line 22.
<>
undef at: {this}{is}{an} at - line 10.
	main::dive(HASH(0x9e47a4), "this", "is", "an", "example") called at - line 23
Use of uninitialized value in printf at - line 23.
<>