I made a Flashlight program.

A program? I thought you wanted to exercise OO? Object properties are usually stored in the object itself, so that you can create multiple instances. If in your program you find that you need another flash light, you'll have to duplicate your entire package, or at least modify it heavily, to support multiple on/off states.

I took the liberty of re-writing it, so you can OO the other machines yourself.

package Flashlight;
use Carp;
use Time::HiRes qw/usleep/;
use strict;

sub new {
    my ($class, %options) = @_;
    my $self = { };
    my @required = qw/color/;
    my @optional = qw/batteries_included type battery_type/;
    for (@required) {
        croak "Required named argument $_ was not defined"
            if not defined $options{$_};
        $self->{$_} = $options{$_};
    }
    for (@optional) {
        $self->{$_} = $options{$_} if exists $options{$_};
    }
    return bless $self, $class;
}

sub color {
    my ($self) = @_;
    return lc $self->{color};
}

sub charge_batteries {
    my ($self, $type) = @_;
    carp 'Please read the manual!'
        if defined $type and $type ne $self->{battery_type};
    return $self->{batteries_included} = 1;
}

sub is_on {
    my ($self) = @_;
    return $self->{on};
}

sub is_off {
    my ($self) = @_;
    return ! $self->{off};
}

sub on {
    my ($self) = @_;
    return undef if not $self->{batteries_included};
    $self->{on} = 1;
    return return 1;
}

sub off {
    my ($self) = @_;
    return $self->{on} = 0;
}

sub switch {
    my ($self) = @_;
    return undef if $self->is_off and not $self->{batteries_included};
    return $self->{on} = ! $self->{on}
}

sub flash {
    my ($self, $duration) = @_;
    croak 'Cannot flash while on' if $self->is_on;
    croak 'Cannot flash for a negative number of seconds' if $duration
+ < 0;
    carp 'flash() should be used to do nothing at all, changing durati
+on'
        if defined $duration and $duration == 0;
    $duration ||= 0.1;
    $self->on();
    usleep $duration;
    $self->off();
}
[download]

Now, it's your turn. I can say only one thing: try harder.

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