How do I include functions from another file in my Perl script?

Question

Hi,

This seems like a really simple question but somehow my Google-Fu failed me.

What's the syntax for including functions from other files in perl? I'm looking for something like C's #include "blah.h"

I saw the option for using perl modules, but that seems like it'll require a not-insignificant rewrite of my current code.

Thanks a bunch!

--Zain

Answer 1

I believe you are looking for the require or use keywords.

Answer 2

You really should look into perl modules however, for a quick hack you could always run "perl -P" which runs your perl script through the C pre-processor. That means you can do #include and friends....

Only a quick hack though, beware ;-)

Answer 3

Perl require will do the job. You will need to ensure that any 'require'd files return truth by adding

1;

at the end of the file.

Here's a tiny sample:

$ cat m1.pl 
use strict;
sub x { warn "aard"; }
1;

$ cat m2.pl 
use strict;
require "m1.pl";
x();

$ perl m2.pl 
aard at m1.pl line 2.

But migrate to modules as soon as you can.

EDIT

A few benefits of migrating code from scripts to modules:

• Without packages, everything occupies a single namespace, so you may hit a situation where two functions from separate files want the same name.
• A package allows you to expose some functions, but hide others. With no packages, all functions are visible.
• Files included with require are only loaded at run time, whereas packages loaded with use are subject to earlier compile-time checks.

Answer 4

Use a module. Check out perldoc perlmod and Exporter.

In file Foo.pm

package Foo;
use strict;
use warnings;
use Exporter;

our @ISA= qw( Exporter );

# these CAN be exported.
our @EXPORT_OK = qw( export_me export_me_too );

# these are exported by default.
our @EXPORT = qw( export_me );

sub export_me {
    # stuff
}

sub export_me_too {
    # stuff
}

1;

In your main program:

use strict;
use warnings;

use Foo;  # import default list of items.

export_me( 1 );

Or to get both functions:

use strict;
use warnings;

use Foo qw( export_me export_me_too );  # import listed items

export_me( 1 );
export_me_too( 1 );

You can also import package variables, but the practice is strongly discouraged.

Answer 5

What are you looking for is 'require file.pl', but what you should be looking at is 'use module'.

Answer 6

Also, do 'file.pl'; will work, but modules are the better solution.