package Package1;
use fields qw(attr1 attr2 attr3);

sub new {
    my Package1 $self = shift;
    $self = fields::new($self) unless ref $self;
    $self->{attr1} = "init_1";
    $self->{attr2} = "init_2";
    $self->{attr3} = "init_3";
    return $self;
}

1;