Re^4: Lexical closures

It's not a bug; it was a deliberate design decision in (I believe) 5.004. Besides, you don't have to put my there. The aliasing works with global variables too:

use 5.010;

package Foo;

use vars '$i';
use strict;
use warnings;

sub bar
{
    for $i (1 .. 10)
    {
        main::baz( $i );
    }
}

package main;

use strict;
use warnings;
use Test::More tests => 12;

$Foo::i = 100;

sub baz
{
    my $expect = shift;
    is( $Foo::i, $expect );
}

baz(100);
Foo::bar();
baz(100);
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Re^5: Lexical closures by backstab (Novice) on Oct 25, 2008 at 21:37 UTC
I think we can also show how the aliased variable can be global with the following, `use vars '$i'; $i = 123; sub foo { my $arg = shift; print "$arg, $i\n"; } foreach $i (0..2) { foo($i); } foo('x'); # obviously alias works only within the loop # Prints, # 0,0 # 1,1 # 2,2 # x,123` [download] If so, I have a question related to my scope. Within the previous example let's declared $i with my instead. `my $i; $i = 123; sub foo { my $arg = shift; print "$arg, $i\n"; } foreach $i (0..2) { foo($i); } foo('x'); # Prints, # 0,123 # 1,123 # 2,123 # x,123` [download] At this point I'm confused in fact. Should not we get the same result? Does not my scope to nested blocks as well? It looks like aliasing does not affect my'd variable despite to be within the same scope or nested scope. The previous result is what I have expected using my on the foreach itself.	[reply] [d/l] [select]
Re^6: Lexical closures by ikegami (Patriarch) on Oct 25, 2008 at 22:33 UTC
In the second snippet, `foo()` captures `$i` since `$i` is a lexical. That means the `$i` in `foo()` will always refer to the specific SV associated with `$i` when `foo` was compiled. When the loop aliases `$i` to a different SV, it doesn't affect `foo`. `use Devel::Peek; my $i; # Lexical variable sub foo { Dump($i); } Dump($i); # SV ... at 0x226048 \ for $i ( 1 ) { # > same foo(); # SV ... at 0x226048 / Dump($i); # SV ... at 0x226d8c }` [download] In the first snippet, there is no closure since `$i` is not a lexical. That means the `foo()` will always grab the current value of `$main::i`. `use Devel::Peek; our $i; # Package variable sub foo { Dump($i); } Dump($i); # SV ... at 0x226d94 for $i ( 1 ) { foo(); # SV ... at 0x226d7c \ same Dump($i); # SV ... at 0x226d7c / }` [download]	[reply] [d/l] [select]