BUILD() method called after object creation? how in perl6?

gistfile1.pl

#! /usr/bin/env perl

use strict;
use warnings;

package Vocab;
use Moose;

my %WORDS;

has 'word'   => ( is => 'ro', required => 1, isa => 'Str' );
has 'synonyms'     => ( is => 'rw', isa => 'ArrayRef[Str]', default => sub { [] } );

sub BUILD {
    my $self = shift;
    my @params = @_;

    foreach my $word ($self->{word}, @{$self->{synonyms}}) {
        $WORDS{$word} ||= [];
        push @{$WORDS{$word}}, $self;
    }
}

sub dump {
    use Data::Dumper;
    print STDERR Dumper(\%WORDS);
}


package Noun;

use Moose;

extends 'Vocab';



package Verb;

use Moose;

extends 'Vocab';



package main;

use Data::Dumper;
Noun->new({word => 'fire', synonyms => ['flame']});
Verb->new({word => 'fire', synonyms => ['launch', 'shoot']});
Verb->new({word => 'fire', synonyms => ['terminate']});


Vocab->dump();