Ever have to give up using a new, really useful feature in Perl
because someone on Centos uses 5.8?

Not sure what will work with PerlBrew if you have five versions
of Perl installed with your modules?

No longer. Now you Makefile.PL can use the correct Perl Version.

This started when I wanted to upgrade FindBin::libs and couldn't
because too many users were stuck on 5.8 (or 5.00503!). I didn't
want to check $^V every time the thing ran, the installed Perl
version isn't going to change with each run. So I copy the
a version of the module for $^V < v5.9 and have another one
that uses newer features.

Upgrading *that* one runs afoul of users on v5.16... Egads! Time
for a module.

Basic use:

(1) Your source code goes into a perl-version-specific directory:

    ./version/v5.8.8/bin/...
    ./version/v5.8.8/lib/...
    ./version/v5.8.8/t/...

    or into Git with tags like

    perl/v5.24
    perl/5.005003
    perl/5.005_003


(2) Your Makefile.PL (or Build.PL or whatever) does a:

    use Module::FromPerlVer;

    use Module::FromPerlVer qw( use_dir 1 );    # copy from dir
    use Module::FromPerlVer qw( use_git 1 );    # checkout with tag

(3) The contents of your install directory are populated
    via bulk copy from ./version of the higest version
    number not greater than the Perl used for installation
    or checkout of tag for the higest Perl version.

For regression testing of current modules with older versions
of Perl you can pass ( perl_version => X ) to ignore $^V and
run the code as if the perl's v-string is X.

The filesystem structure should support any versioning system:
SVN users can simply check out branch tags into ./version or
use "source_dir=branch"; rcs, cvs, or git users can either use
tags or just export the static branches into ./versions. Either
way, the versioning should be straightforward to maintain. The
biggest hurdle is overcoming muscle-memory to edit files under
./lib that are going to be overwritten.

Note that the #! code here uses "#!/usr/bin/env". Some linux 
distros use "/usr/bin" but the stock path in GNU releases and
BSD is /usr/bin with a symlink or copy in /bin. Using the stock
path allows things to run, which seems preferable.

Notes to anyone editing the module:

t/bin/make-*-dir & t/bin/make-tests will set up the test environment
the first time. These are called from Makefile.PL. Running the
Makefile.PL with "TEST_EXTRACT=1" will rm -rf the ./t/version and
and ./t/sandbox/.git dir's to validate the setup code.

