generator_like.pl

use strict;
use warnings;

package Count;

sub new {
    my $class = shift;
    my $start = shift || 0;

    bless { count => $start }, $class;
}

sub next {
    my $self = shift;
    $self->{count}++;
}


package Fib;

sub new {
    my $class = shift;

    bless { seq => [0, 1], count => 0 }, $class;
}

sub next {
    my $self = shift;

    if (scalar @{$self->{seq}} <= $self->{count}) {
        $self->generate;
    }

    $self->{seq}->[$self->{count}++];
}

sub generate {
    my $self = shift;
    $self->{seq}->[ $self->{count} ] 
        = $self->{seq}->[ $self->{count} - 1 ] + $self->{seq}->[ $self->{count} - 2 ]
}

package main;

use Perl6::Say;

my $c = Count->new;
for (0..9) {
    say $c->next;    
}

say;

my $f = Fib->new;
for (0..9) {
    say $f->next;    
}