return \@array or @array

[Yitzchak Scott-Thoennes]

On Thu, Sep 12, 2013 at 7:33 AM, Jérôme Étévé <jerome.eteve at gmail.com> wrote:
> use Devel::Peek;
>
> my $foo_ref;
>
> sub foo{
>     my @foo = 0..2;
>     $foo_ref = \@foo;
>     return @foo;
> }
>
> print Dump([ foo() ]);
> print Dump($foo_ref);
>
> Shows that apparently @foo is deeply copied when it's returned. Is that correct?

No.  But perl notices when you leave foo() that @foo has an external
reference, so it allocates a new one in preparation for the next call
to foo().

> I'm not an expert in perl guts, but it seems there's no such thing as
> a 'list' native structure. They're both PVAV.

The return of a sub isn't a native structure, it's just a range of
elements on a stack.  (So basically a shallow copy, but without an
array container.)  There is no mechanism for returning a PVAV, just a
reference to one.