How can I convert the stringified version of array reference to actual array reference in Perl?

Question

Is there any way to get Perl to convert the stringified version e.g (ARRAY(0x8152c28)) of an array reference to the actual array reference?

For example

perl -e 'use Data::Dumper; $a = [1,2,3];$b = $a; $a = $a.""; warn Dumper (Then some magic happens);'

would yield

$VAR1 = [
      1,
      2,
      3
    ];

Answer 1

Yes, you can do this (even without Inline C). An example:

use strict;
use warnings;

# make a stringified reference
my $array_ref = [ qw/foo bar baz/ ];
my $stringified_ref = "$array_ref";

use B; # core module providing introspection facilities
# extract the hex address
my ($addr) = $stringified_ref =~ /.*(0x\w+)/;
# fake up a B object of the correct class for this type of reference
# and convert it back to a real reference
my $real_ref = bless(\(0+hex $addr), "B::AV")->object_2svref;

print join(",", @$real_ref), "\n";

but don't do that. If your actual object is freed or reused, you may very well end up getting segfaults.

Whatever you are actually trying to achieve, there is certainly a better way. A comment to another answer reveals that the stringification is due to using a reference as a hash key. As responded to there, the better way to do that is the well-battle-tested Tie::RefHash.

Answer 2

The first question is: do you really want to do this?

Where is that string coming from?

If it's coming from outside your Perl program, the pointer value (the hex digits) are going to be meaningless, and there's no way to do it.

If it's coming from inside your program, then there's no need to stringify it in the first place.

Answer 3

Yes, it's possible: use Devel::FindRef.

use strict;
use warnings;
use Data::Dumper;
use Devel::FindRef;

sub ref_again {
   my $str = @_ ? shift : $_;
   my ($addr) = map hex, ($str =~ /\((.+?)\)/);
   Devel::FindRef::ptr2ref $addr;
}

my $ref = [1, 2, 3];
my $str = "$ref";
my $ref_again = ref_again($str);

print Dumper($ref_again);