The London Perl and Raku Workshop takes place on 26th Oct 2024. If your company depends on Perl, please consider sponsoring and/or attending.


Mo - Micro Objects. Mo is less.


    package Less;
    use Mo;
    extends 'Nothing';

    has something => ();


use Mo. Mo is less. Much less.

Moose is huge. Moose led to Mouse led to Moo led to Mo. M is nothing. Mo is more. Not much.

When Moo is more than you need, drop an 'o' and get some Mo.

To get just a little Mo from Mo, use "Mo Features" below.

Core Features

This is what you get. Nothing Mo.

new method

Mo provides a new object constructor. You pass it a list of name/value pairs and it returns a new object.

Constructor will not call BUILD methods. This is available using the Mo::build feature.


Mo exports the extends keyword, to declare your parent class. Mo::Object itself is your default parent class.

Mo only supports single inheritance. If you need multiple inheritance or roles, you should upgrade to Moo.


Mo exports a has keyword, to generate accessors.

These accessors always support both get and set operations. That's it.

    has name => ();
    has thing => (foo => 'bar');  # arguments silently ignored

All arguments passed to has are ignored. This makes it easier to switch between Mo and Moo, without having to change all your accessors.

strict and warnings

Mo turns on use strict and use warnings for you.


Mo is tiny. It is compressed into a single line. You can easily inline it in your code, should you want to do that. See Mo::Inline for more information, including a utility that will do it for you.

Mo Features

Mo is the bare minimum needed for Perl OO. Many times you'll want just a couple more features. Don't worry. Mo's got you covered:

    use Mo qw'build default builder coerce is required';
    has name1 => ( default => sub { 'Joe' } );
    has name2 => ( builder => 'name_builder' );
    has name3 => ( coerce => sub {$_[0]} );
    has name4 => ( is => 'ro' );
    has name4 => ( required => 1 );
    sub BUILD {
        my $self = shift;

Mo simply loads the feature classes Mo::build, Mo::default, Mo::builder, Mo::coerce, Mo::is and Mo::required. The first one supports BUILD constructing and the other three add their magics to has. A Mo::Feature module can enhance new, extends and has, and also add new export subs, or remove existing ones. Features can also be combined for a single accessor. See Mo::Features for a list of all the features and for an explanation of the Feature API..







Build Status


Ingy döt Net <>

Damien 'dams' Krotkine <>

Matt S. Trout (mst) <>

Christian Walde <>

Alessandro Ranellucci (aar/alexrj) <>

Carlos Lima (priodev) <>

Copyright and License

Copyright (c) 2011-2013. Ingy döt Net.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.