All lexical (my) variables are local to the thread they are declared in. Unless they are: Implicitly cloned by being made closures.

Okay, here is a closure:

{
    my $x = 20;

    sub do_stuff {     
        print "$x \n"; 
    }

}

do_stuff();  #$x has gone out of scope here

--output:--
20           #…yet the sub can still see $x
[download]

But in the following thread can the sub see $x because it closes over $x, or can the sub see $x because:

All lexical (my) variables are local to the thread they are declared in. Unless they are: Implicitly cloned because they exist in the spawning thread prior to a 'child' thread being spawned.

use threads;
use threads::shared;


my $x = 20;

sub do_stuff{ 
    print "$x \n";    #closes over $x (as above)
}

threads->create(\&do_stuff)->join();

--output:--
20
[download]

If perl copies all the data to a thread, why doesn't the following code also output 20:

use threads;
use threads::shared;

sub do_stuff{ 
    print "$x \n";   #doesn't close over $x
}

my $x = 20;         

threads->create(\&do_stuff)->join();   #perl copies $x to the thread
                                        

--output:--
<blank line>    #but the thread can't see $x
[download]

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