Why can't localize lexical variable in Perl?

Question

I have below Perl code.

use warnings;
use strict;

my $x = "global\n";



sub a {
    print $x;
}

sub b {
    local $x = "local\n";
    a();
}

a();
b();
a();

Even if $x has scope inside b() subroutine why Perl doesn't allows to localize it ?

Answer 1

You cannot mix the lexical scope used by my with the namespaced global scope of package variables (the keyword local may only be used on the latter). Perl will treat $x in the source as the lexically-scoped variable once you have defined it as such. You can still access the package variable (using $::x) - although that would just mean you had two entirely separate variables in use, and would not allow you to refer to either at the same time as $x.

You can achieve something very similar to what you appear to be trying to do by using our instead of my:

our $x = "global\n";

The our keyword creates a lexically-scoped alias to a package variable.

Output is then:

global
local
global