#!/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.";
        }
    }
}