Alt - Alternate Module Implementations

        PERL_ALT_INSTALL=OVERWRITE cpanm Alt::IO::All::Redux

    "Alt::" is the namespace for alternate implementations of CPAN modules.

    The purpose of the Alt module is to provide documentation explaining the
    Alt concept, how it works, and guidelines for using it well.

    For a given piece of software, CPAN only allows for one implementation
    of a given module/distribution name.

    GitHub on the other hand, is not limited this way. Any author can make a
    fork, since GitHub repos are namespaced by author id.

    On CPAN, even the author(s) of the module in question is limited by
    this, as they cannot release newer or older forks of their code, without
    introducing a new name.

    A module "Foo::Bar" is distributed on CPAN as "Foo-Bar". It may have
    submodules like "Foo::Bar::Baz".

    To make an alternate CPAN version, leave everything exactly the same,
    except distribute the new version as "Alt-Foo-Bar-AltIdentifier".

    When a user installs your module like so:

        PERL_ALT_INSTALL=OVERWRITE cpanm Alt::Foo::Bar::better

    they will get your version of the Foo::Bar framework (Foo::Bar,

    Obviously, this completely overlays the old Foo::Bar install, but that's
    the whole idea. The user isn't surprised by this because they just asked
    for an Alternate implementation. If they don't like it, they can simply
    reinstall the original Foo-Bar, or try some other alternate.

    This idea is new, and the details should be sorted out through proper
    discussions. Pull requests welcome.

    Here are the basic guidelines for best using the Alt namespace:

    Name Creation
        Names for alternate modules should be minted like this:


        For instance, if MSTROUT wants to make an alternate IO-All
        distribution to have it be Moo-based, he might call it:


        He might also just call it:


        By having 'Alt' at the start, it guarantees that it does not mess
        with future IO::All development. The "phrase" at the end can be
        anything unique to CPAN, but should describe the spirit of the
        alternate. If the alternate is meant to be short-lived, it can just
        be the author's CPAN id.

    Makefile.PL Changes
        Due to experience with <> problems, it is
        important to make your Alt module not install without explicit
        direction. You can accomplish this easily in a Makefile.PL, with
        something like this:

            my $alt = $ENV{PERL_ALT_INSTALL} || '';
            $WriteMakefileArgs{DESTDIR} =
              $alt ? $alt eq 'OVERWRITE' ? '' : $alt : 'no-install-alt';

        Similar techniques should be available for other module release

    Module for CPAN Indexing
        You will need to provide a module like "Alt::IO::All::MSTROUT" so
        that CPAN will index something that can cause your distribution to
        get installed by people:


        Since you are adding this module, you should add some doc to it
        explaining your alternate version's improvements.

        The Alt:: module can be as simple as this:

            package Alt::IO::All::MSTROUT;
            our $VERSION = '0.01';

        It is important to use the "no_index" directive on the modules you
        are providing an alternates for. This is especially important if you
        are the author of the original, as PAUSE will reindex CPAN to your
        Alt- version which defeats the purpose. Even if you are not the same
        author, it will make your index reports not show failures.

        It is important to not declare a $VERSION in any of the modules that
        you are providing alternates for. This will help ensure that your
        alternate module does not satisfy the version requirements for
        something that wants the real module.

        If you want to depend on the alternate versions, then set the
        dependency on the "Alt::" module.

        NOTE: If you provide an alternate Foo::Bar (with no VERSION) it will
        satisfy the version requirements for someone who requires "Foo::Bar
        => 0". In a sense, depending on version 0 means that alternates are

    "use" the Alt
        You should add this line to your alternate modules:

            use Alt::IO::All::MSTROUT;

        That way the Alt:: module gets loaded any time you "use IO::All"
        (with the alternate version installed). This gives debugging clues
        since the Alt:: module is now in %INC.

    Other Concerns
        If you have em, I(ngy) would like to know them. Discuss on
        #toolchain on for now.

    The Alt- concept was thought up by Ingy as he tried to figure out how to
    revamp the somewhat popular IO::All and modules. Alternates can
    now be released and alpha/beta tested, while the originals remain

    When Alt-IO-All-new is "community approved" it can replace IO-All. If
    people want the old code, they can can install Alt-IO-All-old.

    Ingy döt Net <>

    Copyright 2012-2014. Ingy döt Net.

    See <>