use 5.028;
use warnings;

package MyCoolRestObject;
use Moose;
use Moose::Util::TypeConstraints;

has body_raw     => ( is => 'ro' );
has url          => ( is => 'ro' );
has datetime     => ( is => 'ro' );
has entry_id     => ( is => 'ro' );
has subject_html => ( is => 'ro' );
coerce 'MyCoolRestObject::Poster' =>
    from 'HashRef' => via { MyCoolRestObject::Poster->new(%$_) };
has poster       => ( is => 'ro',
                      isa => 'MyCoolRestObject::Poster',
                      coerce => 1,
);
coerce 'MyCoolRestObject::Icon' =>
    from 'HashRef' => via { MyCoolRestObject::Icon->new(%$_) };
has icon         => ( is => 'ro',
                      isa => 'MyCoolRestObject::Icon',
                      coerce => 1,
);
has subject_raw  => ( is => 'ro' );
has body_html    => ( is => 'ro' );

# ----------------------------------------------------------------------

package MyCoolRestObject::Icon;
use Moose;

has url          => ( is => 'ro' );
has comment      => ( is => 'ro' );
has picid        => ( is => 'ro' );
has keywords     => ( is => 'ro' );
has username     => ( is => 'ro' );

# ----------------------------------------------------------------------

package MyCoolRestObject::Poster;
use Moose;

has display_name => ( is => 'ro' );
has user_name    => ( is => 'ro' );

# ----------------------------------------------------------------------

package main;
use JSON::PP;
use Data::Dump qw/dump/;
$/ = undef;
my $json = decode_json <DATA>;

my $obj = MyCoolRestObject->new(%$json);
print $obj->icon->username;

__DATA__
{
    "body_raw" : "This is <b>Entry 1</b>",
    "url" : "http://nataraj.nataraj.hack.dreamwidth.net/459.html",
    "datetime" : "2022-08-20 16:36:00",
    "entry_id" : 459,
    "subject_html" : "Entry 1",
    "poster" : {
        "display_name" : "nataraj",
        "username" : "nataraj"
    },
    "icon" : {
        "url" : "http://www.nataraj.hack.dreamwidth.net/userpic/1/3",
        "comment" : "4",
        "picid" : 1,
        "keywords" : [
            "3"
        ],
        "username" : "nataraj"
    },
    "subject_raw" : "Entry 1",
    "body_html" : "This is <b>Entry 1</b>"
}