Question

I created a module Foo::Prototype with the global variables $A and $B. I want the package Foo::Bar that uses Foo::Prototype as a base to import the global variable $A and $B. I could not figure how to do that.

I understand that using global variables is not a good practice in general, but in this case I want to use them.

The code looks like this:

package Foo:Prototype;
my ($A, $B);
our @EXPORT = qw($A $B);

sub new {
    [...]
    $A = 1;
    $B = 2;
}

1;

package Foo:Bar;
use base Foo:Prototype qw($A $B);

sub test {
    print $A, "\n";
    print $B, "\n";
}

1;


# test.pl
Foo:Bar->new();
Foo:Bar->test();

Edit:

I want to make writing sub classes of Foo::Prototype as compact as possible for other people. Instead of having to write $self->{A}->foo(), I’d rather let people write $A->foo().

Answer 1

Well, there are a few of issues:

1. As brian points out, your problem can probably be solved better without using global variables. If you describe what you are trying to achieve rather than how, we may be able to provide better answers.

2. If you are going to export stuff, you either need a sub import or you need to inherit from Exporter. See perldoc Exporter.

3. It is not clear where you want the call to new to occur.

4. As Greg points out in a comment below, variables declared with my at package scope cannot be exported. Therefore, I declared $A and $B using our.

Here is something that “works” but you are going to have to do some reading and thinking before deciding if this is the way you want to go.

T.pm:

package T;
use strict;
use warnings;

use base 'Exporter';

our ($A, $B);
our @EXPORT = qw($A $B);

sub new {
    $A = 1;
    $B = 2;
}

"EOF T.pm"

U.pm:

package U;

use strict;
use warnings;

use base 'T';
use T;

sub test {
    my $self = shift;
    print "$_\n" for $A, $B;
}

"EOF U.pm"

t.pl:

#!/usr/perl/bin
use strict;
use warnings; 

use U;

U->new;
U->test;

C:\Temp> t.pl
1 
2