CODEWITHSUNDEEP
perlscope
Praveen G
Praveen G

Reputation: 11

I am trying to understand the scope of the variable I am using in Perl

I am using this code below in Perl What is the scope of the variable and what does it mean when you say $:: while declaring a variable?

use strict;
use warnings;
use Readonly;

my Readonly::Scalar $::variable_name => 'value';

Thanks in Advance!

Upvotes: 1

Views: 81

Answers (2)

Borodin
Borodin

Reputation: 126722

$::variable_name is identical to $main::variable_name, and you should use the latter for clarity.

You meant either

Readonly::Scalar $main::variable_name => 'value';

which has global scope since $main::variable_name can be accessed from anywhere

or

Readonly::Scalar my $variable_name => 'value';

which has the same scope as a normal my declaration.

Since package variables are generally despised, the latter is preferable; although I realise that it may be useful to be able to access constant values globally

Upvotes: 5

serenesat
serenesat

Reputation: 4709

From perlfaq7:

If you know your package, you can just mention it explicitly, as in $Some_Pack::var. Note that the notation $::var is not the dynamic $var in the current package, but rather the one in the "main" package, as though you had written $main::var.

use vars '$var';
local $var = "global";
my    $var = "lexical";
print "lexical is $var\n";
print "global  is $main::var\n";

Upvotes: 5

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