#! perl
use Modern::Perl;

package Person
{
    use Moose;
    use constant DURATION => 100;

    has use_duration => ( isa => 'Int', is => 'ro', default =>  1, );
    has frequency    => ( isa => 'Int', is => 'ro', default => 50, );
    has number       => ( isa => 'Int', is => 'rw', default =>  0, );

    sub need_to_go
    {
        my ($self) = @_;
        return rand(DURATION) + 1 <= $self->frequency;
    }
}

package Nation
{
    use Moose;

    has population => (
                          isa     => 'ArrayRef[Person]',
                          is      => 'ro',
                          traits  => ['Array'],
                          handles => { obtain => 'push', },
                      );

    sub cull
    {
        use List::MoreUtils qw(part);
        my ($self) = @_;
        my ($keep, $go) = part { $_->need_to_go } @{ $self->population };
        @{ $self->population } = @$keep;
    }

    sub display
    {
        use Data::Dump;
        my ($self, $msg) = @_;
        say "\n$msg\n";
        dd  $self;
    }
}

package main
{
    my $people    = Nation->new;
    my $people_nr = 25;

    for my $case (0 .. $people_nr)
    {
        my $person = Person->new;
        $person->number($case);
        $people->obtain($person);
    }

    $people->display('Before:');
    $people->cull;
    $people->display('After:');
}