#!/usr/bin/env perl -l

use strict;
use warnings;

use IO::Handle;

my $complex_data_hash_ref = {
    not_used_1 => '',
    example => {
        undefined           => undef,
        empty_string        => '',
        non_empty_string    => 'string',
        empty_array_ref     => [],
        non_empty_array_ref => [ 1, 2, 3 ],
        empty_hash_ref      => {},
        non_empty_hash_ref  => { x => 24, y => 25, z => 26 },
        scalar_ref          => \42,
        glob_ref            => \*STDOUT,
        code_ref            => sub { print "\n\t\tHello, world!\n" },
        ref_ref             => \\99,
        blessed_ref         => IO::Handle::->new(),
        ref_ref_ref         => \\\999,
        regex               => qr{match},
        vstring             => v65,
        vstring_ref         => \v65,
    },
    not_used_2 => '',
};

my @example_keys_to_parse = qw{
    undefined empty_string non_empty_string empty_array_ref 
    non_empty_array_ref empty_hash_ref non_empty_hash_ref
    glob_ref code_ref ref_ref blessed_ref ref_ref_ref
    regex vstring vstring_ref
};

for my $example_key (@example_keys_to_parse) {
    my $example_key_value
        = $complex_data_hash_ref->{example}{$example_key};
    examine_data($example_key, $example_key_value);
}

sub examine_data {
    my ($in_key, $in_value) = @_;

    print "Examining '$in_key':";

    if (ref $in_value) {
        print "\tThe value of '$in_key' is a reference.";
        print "\tThe value of '$in_key' is '$in_value'.";

        my $ref = ref $in_value;

        print "\tThe ref() value of '$in_key' is '$ref'.";

        if ($ref eq 'SCALAR') {
            my $deref = ${$in_value};
            print "\tIts dereferenced value is '$deref'.";
        }
        elsif ($ref eq 'ARRAY') {
            my @deref = @{$in_value};

            if (@deref) {
                print "\tIts dereferenced value has these elements: ",
                        "'@deref'.";
            }
            else {
                print "\tIts dereferenced value has no elements.";
            }
        }
        elsif ($ref eq 'HASH') {
            my %deref = %{$in_value};
            my @deref_keys = keys %deref;

            if (@deref_keys) {
                print "\tIts dereferenced value has these keys: ",
                        "'@deref_keys'.";

                my @deref_values = values %deref;

                print  "\tIts dereferenced value has these values: ",
                        "'@deref_values'.";
            }
            else {
                print "\tIts dereferenced value has no key-value pairs.";
            }
        }
        elsif ($ref eq 'GLOB') {
            print $in_value "\tA globref can be a filehandle opened for writing.";
        }
        elsif ($ref eq 'CODE') {
            $in_value->();
        }
        elsif ($ref eq 'REF') {
            examine_data('dereferenced__' . $in_key, ${$in_value});
        }
        else {
            print "\tTODO: Further work on this type ",
                    'is left as an exercise for the reader.';
        }
    }
    else {
        print "\tThe value of '$in_key' is not a reference.";

        if (defined $in_value) {
            print "\tThe value of '$in_key' is defined.";

            if (length $in_value) {
                print "\tThe value of '$in_key' is '$in_value'.";
            }
            else {
                print "\tThe value of '$in_key' is zero-length.";
            }
        }
        else {
            print "\tThe value of '$in_key' is not defined.";
        }
    }
}

##</code><code>##

Examining 'undefined':
	The value of 'undefined' is not a reference.
	The value of 'undefined' is not defined.
Examining 'empty_string':
	The value of 'empty_string' is not a reference.
	The value of 'empty_string' is defined.
	The value of 'empty_string' is zero-length.
Examining 'non_empty_string':
	The value of 'non_empty_string' is not a reference.
	The value of 'non_empty_string' is defined.
	The value of 'non_empty_string' is 'string'.
Examining 'empty_array_ref':
	The value of 'empty_array_ref' is a reference.
	The value of 'empty_array_ref' is 'ARRAY(0x7fdcfe8040b0)'.
	The ref() value of 'empty_array_ref' is 'ARRAY'.
	Its dereferenced value has no elements.
Examining 'non_empty_array_ref':
	The value of 'non_empty_array_ref' is a reference.
	The value of 'non_empty_array_ref' is 'ARRAY(0x7fdcfe82bf58)'.
	The ref() value of 'non_empty_array_ref' is 'ARRAY'.
	Its dereferenced value has these elements: '1 2 3'.
Examining 'empty_hash_ref':
	The value of 'empty_hash_ref' is a reference.
	The value of 'empty_hash_ref' is 'HASH(0x7fdcfe82c048)'.
	The ref() value of 'empty_hash_ref' is 'HASH'.
	Its dereferenced value has no key-value pairs.
Examining 'non_empty_hash_ref':
	The value of 'non_empty_hash_ref' is a reference.
	The value of 'non_empty_hash_ref' is 'HASH(0x7fdcfe82c0f0)'.
	The ref() value of 'non_empty_hash_ref' is 'HASH'.
	Its dereferenced value has these keys: 'y z x'.
	Its dereferenced value has these values: '25 26 24'.
Examining 'glob_ref':
	The value of 'glob_ref' is a reference.
	The value of 'glob_ref' is 'GLOB(0x7fdcfe82c2d0)'.
	The ref() value of 'glob_ref' is 'GLOB'.
	A globref can be a filehandle opened for writing.
Examining 'code_ref':
	The value of 'code_ref' is a reference.
	The value of 'code_ref' is 'CODE(0x7fdcff08c5a0)'.
	The ref() value of 'code_ref' is 'CODE'.

		Hello, world!

Examining 'ref_ref':
	The value of 'ref_ref' is a reference.
	The value of 'ref_ref' is 'REF(0x7fdcfe82c1b0)'.
	The ref() value of 'ref_ref' is 'REF'.
Examining 'dereferenced__ref_ref':
	The value of 'dereferenced__ref_ref' is a reference.
	The value of 'dereferenced__ref_ref' is 'SCALAR(0x7fdcff07b598)'.
	The ref() value of 'dereferenced__ref_ref' is 'SCALAR'.
	Its dereferenced value is '99'.
Examining 'blessed_ref':
	The value of 'blessed_ref' is a reference.
	The value of 'blessed_ref' is 'IO::Handle=GLOB(0x7fdcfe82c240)'.
	The ref() value of 'blessed_ref' is 'IO::Handle'.
	TODO: Further work on this type is left as an exercise for the reader.
Examining 'ref_ref_ref':
	The value of 'ref_ref_ref' is a reference.
	The value of 'ref_ref_ref' is 'REF(0x7fdcfe82c480)'.
	The ref() value of 'ref_ref_ref' is 'REF'.
Examining 'dereferenced__ref_ref_ref':
	The value of 'dereferenced__ref_ref_ref' is a reference.
	The value of 'dereferenced__ref_ref_ref' is 'REF(0x7fdcfe84b2d0)'.
	The ref() value of 'dereferenced__ref_ref_ref' is 'REF'.
Examining 'dereferenced__dereferenced__ref_ref_ref':
	The value of 'dereferenced__dereferenced__ref_ref_ref' is a reference.
	The value of 'dereferenced__dereferenced__ref_ref_ref' is 'SCALAR(0x7fdcfe8441c8)'.
	The ref() value of 'dereferenced__dereferenced__ref_ref_ref' is 'SCALAR'.
	Its dereferenced value is '999'.
Examining 'regex':
	The value of 'regex' is a reference.
	The value of 'regex' is '(?^:match)'.
	The ref() value of 'regex' is 'Regexp'.
	TODO: Further work on this type is left as an exercise for the reader.
Examining 'vstring':
	The value of 'vstring' is not a reference.
	The value of 'vstring' is defined.
	The value of 'vstring' is 'A'.
Examining 'vstring_ref':
	The value of 'vstring_ref' is a reference.
	The value of 'vstring_ref' is 'VSTRING(0x7fdcff02e130)'.
	The ref() value of 'vstring_ref' is 'VSTRING'.
	TODO: Further work on this type is left as an exercise for the reader.