Installing Perl5 modules locally
Normally, the perl5 module installation procedure includes commands something like these:

  % perl5 Makefile.PL
  % make
  % make test
  % make install

The first command, perl5 Makefile.PL, directs perl5 to create a makefile for the new module you are installing. When installing a perl5 module locally you must designate on the command line the home directory of your perl5 installation. That information is used by perl5 to create the makefile. Substitute the following command for perl5 Makefile.PL:

  % perl5 Makefile.PL PREFIX=/usr/home/<username>/usr/local

The value <username> above should be replaced with the username of your Virtual Server. So the complete installation process is:

  % perl5 Makefile.PL PREFIX=/usr/home/<username>/usr/local
  % make      
  % make test      
  % make install      

For older modules it may be necessary to designate several other variables on the command line during the module installation:

  % perl5 Makefile.PL PREFIX=/usr/home/<username>/usr/local \
     INSTALLPRIVLIB=/usr/home/<username>/usr/local/lib/perl5 \
     INSTALLSCRIPT=/usr/home/<username>/usr/local/bin \
     INSTALLSITELIB=/usr/home/<username>/usr/local/lib/perl5/site_perl \
     INSTALLBIN=/usr/home/<username>/usr/local/bin \
     INSTALLMAN1DIR=/usr/home/<username>/usr/local/lib/perl5/man \
     INSTALLMAN3DIR=/usr/home/<username>/usr/local/lib/perl5/man/man3 

To save yourself some typing you can create a file and put these variable assignments above in the file (<filename>) something like this:

  PREFIX=/usr/home/<username>/usr/local \
  INSTALLPRIVLIB=/usr/home/<username>/usr/local/lib/perl5 \
  INSTALLSCRIPT=/usr/home/<username>/usr/local/bin \
  INSTALLSITELIB=/usr/home/<username>/usr/local/lib/perl5/site_perl \
  INSTALLBIN=/usr/home/<username>/usr/local/bin \
  INSTALLMAN1DIR=/usr/home/<username>/usr/local/lib/perl5/man \
  INSTALLMAN3DIR=/usr/home/<username>/usr/local/lib/perl5/man/man3

Then, each time you install a perl5 module you can use the following syntax:

  % perl5 Makefile.PL `cat <filename>` 
  % make    
  % make test 
  % make install

You also can have a few different local modules installation procedures, for example one for production perl and another for development:

  % perl5 Makefile.PL `cat <filename>.production`

or

  % perl5 Makefile.PL `cat <filename>.development`

Making scripts find the modules you have installed
When you install perl5 on your Virtual Server, all pre-installed modules are installed into these 4 directories (depending on which version of perl5 you are installing):

  /usr/lib/perl5
  /usr/lib/perl5/i386-bsdos/5.00X
  /usr/lib/perl5/site_perl/i386-bsdos
  /usr/lib/perl5/site_perl

These 4 directories are already preset in the perl5's @INC array. That array contains the paths that perl5 searches in order to find modules. If you install perl5 modules locally as described above, you will need to append these two directories, which are local to your Virtual Server, to the @INC array:

  /usr/home/<username>/usr/local/lib/perl5
  /usr/home/<username>/usr/local/lib/perl5/site_perl

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:

  use lib qw(/usr/home/<username>/usr/local/lib/perl5 
             /usr/home/<username>/usr/local/lib/perl5/site_perl);

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:

  BEGIN { unshift @INC, qw(/usr/home/<username>/usr/local/lib/perl5
                           /usr/home/<username>/usr/local/lib/perl5/site_perl); }

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
Okay, imagine that you have installed module A in /usr/home/<username>/usr/local/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. Perl5 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:

  % setenv PERL5LIB \
    /usr/home/<username>/usr/local/lib/perl5:/usr/home/<username>/usr/local/lib/perl5/site_perl

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 perl5 modules is the CPAN.pm module (see www.perl.com/CPAN/) which automates module download and installation. If you have perl5.004 or higher installed you have it bundled with the distribution. If not, you can download it from CPAN.

When you install it or use it the first time, the module asks you a few questions, one of which is a PREFIX directory as described above (so you can define a different PREFIX directory if you will be doing local installations).

After configuration of the module is complete, you run it like this:

  % perl5 -MCPAN -e shell
  > install CGI

It will fetch the latest 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:

  > i /CGI/ 

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 perldoc CPAN to read the man page.