In Perl, how can I find out if my file is being used as a module or run as a script?

Question

Let\'s say I have a Perl file in which there are parts I need to run only when I\'m called as a script. I remember reading sometime back about including those parts in a mai

Answer 1

Better to not do this, and instead take a structured approach like MooseX::Runnable.

Your class will look like:

class Get::Me::Data with (MooseX::Runnable, MooseX::Getopt) {

    has 'dsn' => (
        is            => 'ro',
        isa           => 'Str',
        documentation => 'Database to connect to',
    );

    has 'database' => (
        is         => 'ro',
        traits     => ['NoGetopt'],
        lazy_build => 1,
    );

    method _build_database {
        Database->connect($self->dsn);
    }

    method get_data(Str $for_person){
        return $database->search({ person => $for_person });
    }

    method run(Str $for_person?) {
        if(!$defined $for_person){
            print "Type the person you are looking for: ";
            $for_person = <>;
            chomp $for_person;
        }

        my @data = $self->get_data($for_person);

        if(!@data){
            say "No data found for $for_person";
            return 1;
        }

        for my $data (@data){
            say $data->format;
        }

        return 0;
    }
}

Now you have a class that can be used inside your program easily:

my $finder = Get::Me::Data->new( database => $dbh );
$finder->get_data('jrockway');

Inside an interactive script that is bigger than just the "run" method above:

...
my $finder = Get::Me::Data->new( dsn => 'person_database' );
$finder->run('jrockway') and die 'Failure'; # and because "0" is success
say "All done with Get::Me::Data.";
...

If you just want to do this standalone, you can say:

$ mx-run Get::Me::Data --help
Usage: mx-run ... [arguments]
    --dsn     Database to connect to

$ mx-run Get::Me::Data --dsn person_database
Type the person you are looking for: jrockway


$ mx-run Get::Me::Data --dsn person_database jrockway

Notice how little code you wrote, and how flexible the resulting class is. "main if !caller" is nice, but why bother when you can do better?

(BTW, MX::Runnable has plugins; so you can easily increase the amount of debugging output you see, restart your app when the code changes, make the app persistent, run it in the profiler, etc.)