I tought there was a function in Scalar::Util that returns the refcount of an object, but I couldn't find it. But also in Scalar::Util, you find the weaken function, which lets you pass around weak references. From your description, I think you have a "master" object that holds all "relevant" children, but over time, some of the children become irrelevant yet are kept alive by some references. If you make your master hold strong (normal) references but pass out only weak references, your children will be removed if the master removes them from the list.

Such an approach will have different problems, because weak references can turn into strong references again if you copy them, unfortunately. Maybe another approach would be to (always) ask the master whether a child is still relevant or not ...

I'm just curious, is the only way to make a weak reference strong, by copying it ?

$y = \($$y) ;
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LuCa

I wouldn't call that copying. Your snippet creates a new reference. And yes, that works.

/* generated by h2xs -c Scalar::RefCount */
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#include "ppport.h"



MODULE = Scalar::RefCount       PACKAGE = Scalar::RefCount

int
refcount(s)
    SV* s
PROTOTYPE: $
CODE:
    RETVAL = SvREFCNT(s);
OUTPUT:
    RETVAL
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use Test::More tests => 6;
BEGIN { use_ok('Scalar::RefCount') };

#########################

my $a;

is(Scalar::RefCount::refcount($a),1, 'return 1');

my $b = \$a;
is(Scalar::RefCount::refcount($a),2, 'return 2');

my $c = \$a;
is(Scalar::RefCount::refcount($a),3, 'return 3');

{
my $d = \$a;
is(Scalar::RefCount::refcount($a),4, 'return 4');
}
is(Scalar::RefCount::refcount($a),3, 'return 3');
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SvREFCNT is exposed in Devel::Peek (no need to go to CPAN), which is a bit easier to use than embedding XS. For example:

use Devel::Peek qw(SvREFCNT);

$x = 42;
$y = \$x;

$refs_for_x = SvREFCNT($x);
print "$refs_for_x\n";
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Prints 2.

Otherwise, it seems an unusual route to go down and that makes me think it might not be the right path. Could you let us know more about your motivation for this, so we can offer an opinion on this?

See Internals::GetRefCount($object) for direct access to refcounts without writing your own XS.

Your statement:

I only want to use those objects which are referenced

I simply wanted to point that out; perhaps it was just a miscommunication. If weaken was what you were looking for, great.