Using the Alternate Library Location (Learning Perl Objects, References & Modules)

13.10. Using the Alternate Library Location

The libraries are installed relative to the PREFIX specified earlier. If Ginger used a PREFIX of /home/ginger/Testing, you need to add the appropriate directory below it to the search path. The use lib directive of:

use lib "/home/ginger/Testing/lib/site_perl";

does the right thing to find the version-specific directory below it, as well as the architecture-specific directory below it, if needed (usually for architecture-specific files, such as compiled binaries).

You can also specify the include directory on the command line with a -M option:

$ perl -Mlib=/home/ginger/Testing/lib/site_perl myproggy

or a -I option:

$ perl -I /home/ginger/Testing/lib/site_perl myproggy

or even by setting the PERL5LIB environment variable (using sh-like syntax here):

$ PERL5LIB=/home/ginger/Testing/lib/site_perl; export PERL5LIB
$ ./myproggy

However, the downside of any of these methods (other than the use lib method) is that they require you to do something more than just execute the file. If someone (or something) else (such as a coworker or a web server) executes your program, it's unlikely that the proper environment variable or command-line option will be present. Your program will fail because it can't find your locally installed module.

Use use lib, when you can. The other ways are useful mainly for trying out a new version of an old module before replacing the old module (and possibly breaking the programs that use it).