#!/usr/bin/env perl

use 5.012;
use warnings;

use Data::Dump qw/dump dumpf/;

# This simulates the "resource" key you mentioned in (3)
my $singleton = bless({ 
    note => 'Defined outside $hairy_object', 
    1..20 # To really drive the point home :-)
}, 'Singleton::Resource');

# A reasonably complex object, just enough to illustrate.
my $hairy_object = bless {
    attr1     => 'val1',
    resource  => $singleton,
    unwanted  => bless({ thing => 'We want to ignore' }, 'Unwanted'),
    however   => { this => {
        unwanted => bless({ is => 'actually wanted' }, 'Unwanted'),
    }},
    Silly => {
        complex => {
            references => 'can be mangled',
            so => "they make more sense.",
        }
    }
}, 'Hairy::Object';
# Throw in a couple of circular references
$hairy_object->{circular_ref} = $hairy_object;
$hairy_object->{internal_ref} = $hairy_object->{however}{this};

say "Before:";
say '-' x 76;
say dump($hairy_object);
say "\nAfter:";
say '-' x 76;

$Data::Dump::INDENT = '   '; # Edit to taste. '|  ' is nice, too.

# Set up callback; called for every node in the $hairy_object tree
# This is the heart of the logic that controls the dumpf() output
my $dump = dumpf($hairy_object, sub {
    no warnings 'uninitialized';
    my ($ctx, $obj) = @_;

    my %r;

    if ($ctx->depth == 0) {
        $r{hide_keys} = [ grep {
            ref($obj->{$_}) =~ /^(Unwanted|Something::Else)$/;
        } keys %$obj ];
});

# Munge the resulting dump a bit to remove extraneous bits
$dump =~ s/^\Q$Data::Dump::INDENT\E//mg; # Remove one indent
$dump =~ s/\Ado \{.+?my \$a = bless\(\{\n//s;
$dump =~ s/\$a;\n\}//ms;

say "\$a = bless( {\n$dump";