Using global variables with strict pragma in Perl

Question

I was wondering if I could use some globals variables while using strict pragma.

For example, I've tried to do this:

#!/usr/bin/perl -w

use strict;

sub print_global{
     print "your global is: $global\n";
}

$global = 1234;     #or even my $global = 1234;

print_global;

But as you can notice it doesn't work.

Are there any ways to define global variables when using strict pragma? (if any, of course)

score 6 · Accepted Answer · answered Jul 10 '13 at 10:58

6

Just declare the global before using it:

our $global;

Unlike my, this does not create a new variable, but rather makes the variable available in this scope. So you could safely have code like

sub print_global{
     our $global;  # does not create a new variable like `my` would
     print "your global is: $global\n";
}

our $global = 1234;

print_global;

answered Jul 10 '13 at 10:58

amon

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Please, say me what you intend for creating: declaring or defining? – Acsor Jul 10 '13 at 12:24

score 1 · Answer 2 · answered Jul 10 '13 at 10:58

1

Declare my $global; above your function and it'll work with use strict;.

answered Jul 10 '13 at 10:58

mpapec

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Yeah, it works. But didn't my keyword modified scope between functions? Why is my $global also visible to other subroutines declaring it above? – Acsor Jul 10 '13 at 11:04
variables declared with `my` in most outer scope are visible to all below code regardless if in subroutine or not. – mpapec Jul 10 '13 at 11:05
Ok but, how is it possible the example above? – Acsor Jul 10 '13 at 11:08
check `my` vs `our` and how they actually behave http://stackoverflow.com/a/885888/223226 – mpapec Jul 10 '13 at 11:10
2

`our` variables always reference the fully qualified package variable `${__PACKAGE__}::VariableName` which is not lexically scoped like a `my` variable. What is lexically scoped is the alias `$VariableName`. – Joel Berger Jul 10 '13 at 11:52
Thanks to both. I had forgotten that my variables are only scoped to the enclosing block and that you can define subroutines everywhere in the code. – Acsor Jul 10 '13 at 12:18

score 1 · Answer 3 · answered Jul 10 '13 at 11:32

use strict; tells Perl you wish to be forced to declare your variables, and you did not do so. Add a declaration where appropriate.

#!/usr/bin/perl -w

use strict;

my $global;     # <----

sub print_global{
     print "your global is: $global\n";
}

$global = 1234;
print_global;

Using global variables with strict pragma in Perl

3 Answers3