FAQ 3.4 How do I find which modules are installed on my system?

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3.4: How do I find which modules are installed on my system?

    From the command line, you can use the "cpan" command's "-l" switch:

            $ cpan -l
    You can also use "cpan"'s "-a" switch to create an autobundle file that
    "CPAN.pm" understands and cna use to re-install every module:

            $ cpan -a
    Inside a Perl program, you can use the ExtUtils::Installed module to
    show all installed distributions, although it can take awhile to do its
    magic. The standard library which comes with Perl just shows up as
    "Perl" (although you can get those with Module::CoreList).

            use ExtUtils::Installed;

            my $inst    = ExtUtils::Installed->new();
            my @modules = $inst->modules();

    If you want a list of all of the Perl module filenames, you can use

            use File::Find::Rule;

            my @files = File::Find::Rule->
                    extras({follow => 1})->
                    name( '*.pm' )->
                    in( @INC )

    If you do not have that module, you can do the same thing with
    File::Find which is part of the standard library.

            use File::Find;
            my @files;

                    wanted => sub {
                        push @files, $File::Find::fullname
                            if -f $File::Find::fullname && /\.pm$/
                    follow => 1,
                    follow_skip => 2,

            print join "\n", @files;

    If you simply need to quickly check to see if a module is available, you
    can check for its documentation. If you can read the documentation the
    module is most likely installed. If you cannot read the documentation,
    the module might not have any (in rare cases).

            $ perldoc Module::Name

    You can also try to include the module in a one-liner to see if perl
    finds it.

            $ perl -MModule::Name -e1


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