I thought CGI.pm came bundled with Perl.

Yes. I don’t use Fedora, but according to the Fedora Project wiki, Fedora 16 features 100% “Update Perl to 5.14.”, and from perldoc it appears that CGI is a core module in Perl 5.14.0.

How do I know if a particular module is installed on my system?

See the FAQ http://perldoc.perl.org/perlfaq3.html#How-do-I-find-which-modules-are-installed-on-my-system%3f, or this PerlMonks node from 2005: Finding All Installed Modules.

What is best way to install Perl modules?

I find cpanm works fine. See http://www.cpan.org/modules/INSTALL.html, http://search.cpan.org/~miyagawa/App-cpanminus-1.5013/bin/cpanm, and http://bouncehammer.jp/en/email-topics/2011/06/install-perl-modules-using-cpanm-command.html. (But I’m on Windows, and YMMV.)

HTH,

What is best way to install Perl modules?

You may want to use the modules shipped by your distro, so that they're updated automatically when you run an update of your system,
although they're generally slightly older than the most recent modules you can find on CPAN.

Try a
yum search perl | less
or
yum search perl MODULENAME
to find out if a module is available on Fedora as a separate module.

Also,
rpm -qa | grep perl
may help you find out what modules you have installed (this will not list core modules or modules you installed via CPAN, though).

I find modules installed via yum more manageable, but it's just a matter of taste.
I fallback to CPAN whenever I need the latest version of a module or a module which is not packaged with the distro, although this rarely happens.

Yes, CGI.pm does come bundled with Perl.

1. You can find out if a file exists on your system using:

locate -b CGI.pm
[download]

(Note that locate doesn't really search the file system - it searches an index of the file system, which is usually configured to be updated on a nightly basis, so results can be up to 24 hours out of date.)

To know if a module is installed in a place where Perl can find it, use:

perl -e1 -MCGI
[download]

This will print nothing if CGI can be loaded; and print an error if it cannot.

There's also a module called V which is pretty handy. It allows you to type this:

perl -MV=CGI
[download]

... and it will tell you what version number of CGI.pm you have installed.

2. App::cpanminus is a pretty good CPAN client. And Fedora probably makes a large number of Perl modules available via their own packaging system (yum if I recall correctly).