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How do you create a Perl module?

Asked 2009-02-15T12:53:07.603
17

How do you write a module for Perl? In Python you can use: 

# module.py
def helloworld(name):
    print "Hello, %s" % name

# main.py
import module
module.helloworld("Jim")
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6

One minor detail that the answers so far haven't mentioned is that, if you have a (preferably small) module which is purpose-specific enough that it will never be reused, you can put it into the same file as the main program or another package:

# main.pl

# Since this is a beginner question, I'll also point out that you should
# *always* use strict and warnings.  It will save you many headaches.
use strict;
use warnings;

MyModule::helloworld('Jim');
AnotherModule::helloworld('Jim');

package MyModule; # Still in main.pl!

sub helloworld { 
    my ( $name ) = @_;
    print "Hello, $name\n";
}

package AnotherModule; # Yep, still main.pl

sub helloworld {
    my $name = shift;
    print "Another hello to $name\n";
}

This isn't used often because it gives you a package that's defined in a file whose name isn't the same as the package's, which can get confusing because you have to use/require the filename, but reference it in code by the package name.

Also note that the 1; is only needed as the final line of each file which is included via use/require. In this case, I didn't need it because it's in main.pl. If you put multiple packages into the same file, you only need a 1; at the end of the file, not after each package.

answered 2009-02-15T14:20:49.903

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