Mac Forum / Programming / Perl / October 2005

If you run:

    % perl -V

you'll see (at the end) @INC, the list of directories that perl will  
search for modules.  First comes the standard ones in /System/Library/
Perl, then the place for user-installable modules in /Library/Perl.  /
Network/Library/Perl might be used by organizations with fileservers  
that want to have a central place for their modules.

Then there is the /System/Library/Perl/Extras directories that Apple  
uses for third party modules it ships.  Finally you should see /
Library/Perl/5.8.1, which is for compatibility with previous user-
installed modules, as in your case.

So you should be fine with perl finding your 5.8.1 modules, as they  
should be compatible.  If you find that any needs to be updated, they  
should automatically go into /Library/Perl/5.8.6 when installed,  
overriding the older ones in /Library/Perl/5.8.1.  Over time, you  
should be able to clean out the old modules as new ones go in.

Edward Moy
Apple

P.S.  Note that the Extras and 5.8.1 directories are controlled by  
the file /Library/Perl/5.8.6/AppendToPath, a feature added by Apple  
to simulate the effect if you had actually compiled perl 5.8.6  
yourself, as it would automatically see the old 5.8.1 directories and  
compile those in.  You can add your own paths to this file if you  
want to append paths to @INC systemwide.  If you create a file /
Library/Perl/5.8.6/PrependToPath, then those paths will be added to  
the beginning of @INC systemwide.

If you ever have a need to run a stock perl installation (assuming  
you haven't installed anything in /System/Library/Perl), you can move  
the /Library/Perl/5.8.6/AppendToPath file aside (just remember to put  
it back afterwards).  This might be useful for developers who want to  
make sure that their code will run on a stock perl installation, or  
to see what additional modules their code depends on.