Perl on Mac OS 10.10 Yosemite with strange @INC path

osx-yosemiteperl

After upgrading to OS 10.10 I had to install all former used perl modules again. No problem. I thought.

Perl on OS 10.10 is "This is perl 5, version 16, subversion 3 (v5.16.3) built for darwin-thread-multi-2level" (from perl –version).
The @INC looks to be (try perl -e 'print join("\n", @INC);' or perl -V):

/opt/local/lib/perl5/site_perl/5.16.3/darwin-thread-multi-2level
/opt/local/lib/perl5/site_perl/5.16.3
/opt/local/lib/perl5/vendor_perl/5.16.3/darwin-thread-multi-2level
/opt/local/lib/perl5/vendor_perl/5.16.3
/opt/local/lib/perl5/5.16.3/darwin-thread-multi-2level
/opt/local/lib/perl5/5.16.3
/opt/local/lib/perl5/site_perl
/opt/local/lib/perl5/vendor_perl

When I try to use an unknown module, perl throws:
"Can't locate Mymodule.pm in @INC … and then: @INC contains: … /Library/Perl/5.18/darwin-thread-multi-2level /Library/Perl/5.18 /Network/Library/Perl/5.18/darwin-thread-multi-2level /Network/Library/Perl/5.18 and all other known (and added 5.18 perl.pm folders).
Every perl dev knows that message.
But read literally: @INC links obviously to 5.18 folders ! And at a first glance I supposed to use Perl 5.18.

I installed my first bunch of new modules from Macports. 5.18 portfiles. And added the new module pathes to the list /Library/Perl/5.18/AppendToPath. Worked well.
But when I installed a module – not available as 5.18 in Macports – with cpan, I got trouble. The module was compiled with 5.16 (of course, see above) and was not accepted as other path in the AppendToPath file. Dynaloader mismatch.

I do not know, where the @INC list is altered at runtime. In earlier Mac OS 10 versions, the new @INC included same version module versions. I.e. an active perl 5.14 included also 5.14 modules, 5.12 included 5.12 pathes a.s.o.
Why does perl 5.16 on Yosemite include 5.18 module pathes ?

To add some confusion after my post:
When I try a print $^V in program code, I get 5.18.
That means, you don't get what you meant to get. May be my shebang #!/usr/bin/perl starts 5.18 and not 5.16.

Best Answer

Experienced Perl developers will tell you to ignore the system perl. If you upgrade it, for a bugfix you need, you run the risk of breaking your OS. If you upgrade your OS, a modified system perl may break your code.

Macports and homebrew are both great, but not ideal for Perl. I'd clear the /opt/local/version from my PATH, or even my system.

Do yourself a big favor. Install Xcode with the Command Line Tools. Install perlbrew. Roll up your own perl. Heck, roll up 6 of your own perls and jump back and forth between them. Keep a threaded version around for when you need it. Keep a non-threaded around for speed. Best of all, whenever you change which version you are using, perlbrew updates your environment correctly for you. No fuss, No muss.

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