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| How to
Install Your Own Perl Modules Because we typically have just the standard Perl 5 modules installed there may be times when you need the functionality of a module we don't have installed. Keeping various modules updated for everyone without breaking everyone's scripts would be difficult. Below you'll find some information that should make using these modules easier my allowing you to install the module into your own directory space. Installing Perl 5 Modules Locally Installing Perl 5 modules yourself can be a tricky exercise. Utilities for installing Perl 5 modules generally assume that the installation is being done in the root area of the file system of the host machine. As a user you do not have access to the root area of the host machine. So, you must install Perl 5 modules locally, within your directory space. Normally, the Perl 5 module installation procedure includes commands something like these:
The first command, "perl Makefile.PL", directs Perl to create a Makefile for the new module you are installing. When installing a Perl module locally you must designate on the command line the directory of your local Perl module directory. That information is used by Perl 5 to create the Makefile. Substitute the following command for "perl Makefile.PL":
The value <homedir> above should be replaced with the output from the following UNIX command:
So the complete installation process is:
For older modules it may be necessary to designate several other variables on the command line during the module installation:
To save yourself some typing you can create a file and put these variable assignments above in a file (perlmodvars) something like this:
Then, each time you install a Perl module you can use the following syntax:
You also can have a few different local modules installation procedures, for example one for production Perl and another for development:
Making Scripts Find the Modules You Have Installed All pre-installed modules are installed into these 4 directories (depending on the version of Perl):
These 4 directories are already preset in the Perl 5 @INC array. That array contains the paths that perl searches in order to find modules. If you install perl modules locally as described above, you will need to append these two directories, which are local to your directory space, to the @INC array:
The architecture specific directories are being searched by Perl automatically Each time you want to use modules in that path you should add the following line to your scripts:
You don't have to put it into a BEGIN block; the lib.pm module takes care of that for you. It also adds the architecture specific directories. You also can use a BEGIN block to include your installed modules:
However, the use lib construct seems to be cleaner and the unshift @INC construct doesn't automatically add the architecture specific directories to the @INC array. Installing New Modules that Require Locally Installed Modules Imagine that you have installed module A in <homedir>/perl/lib/perl5. Now you want to install a module B that demands module A to be already installed. You know that you have installed the A module, but amazingly B can't locate it. Why? Because when you try to install the module B it doesn't know that you have module A installed locally. Perl 5 searches the basic 4 directories as defined by default in the @INC array. But your local directories aren't listed there. The solution is simple. The PERL5LIB environment variable does the same job in the shell as use lib does in your script. So if you use csh/tcsh type the following at the command line:
Check the man page of your favorite shell how to set the environment variables if you use a shell different from csh/tcsh. Put this setenv statement into .login or another file that is being sourced each time you login into your account and you will not have to worry to remember setting it each time you login. Module Installation Using CPAN.pm An alternative to manually installing Perl modules is the CPAN.pm module (see www.perl.com/CPAN/) which automates module download and installation. When you initially run the
command, it will ask you a few questions. You can use all the defaults, except for this one
and this one: When it asks for your favorite CPAN site, try this:
After configuration of the module is complete, you will see a
> prompt.
It will fetch the latest version of the CGI module, unpack it, make it, test it and install it into your local area, or the directory you specified as the PREFIX directory. The command:
will return the list of modules that match that pattern. The CPAN.pm module has more functionality, like checking for the latest modules, for example. Just run
to read the man page. An Actual Example Install In this example we needed the HTTP-Lite Perl module to do some data acquisition from within a Perl script. Login to our account
Create our local Perl directory
Create the directory to store the module source
Create our "perlmodvars" file (using vi or your favorite editor)
Download the module using lynx, gunzip, and untar the file
Make the new module
View the man page for the new module
Modify the @INC array in the perl script in which we want to use the module
Run the new script:
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