in reply to dereferencing a stringfied referent

You can't, at least not easily. Sure, you could write some XS code that puts the address back into the RV field of a reference, but you're not meant to mess with addresses like in C.  It's asking for trouble, because Perl manages memory via reference counts1. And what if the item your stringified "reference" points to no longer exists when you dereference it?

What is the real problem you're trying to solve, for which you would need this functionality?

___

1 those reference counts are automatically incremented/decremented as needed as long as you use normal Perl references, but they're not updated for stringified references.

  • Comment on Re: dereferencing a stringfied referent

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Re^2: dereferencing a stringfied referent
by clueless newbie (Curate) on Jun 12, 2010 at 13:02 UTC
    Hi,

    I'm working with a SIG{__WARN__} and I'm calling Carp::Longmess. By default, I'm getting those lovely stringified referents which I want. But I also need to get the data structures those stringified referents dereference to.

    I suppose I could get Carp::Longmess to expand out the un blessed data structures then capture them via "regex", but I was hoping that there was a cleaner way.

[reply]
Re^2: dereferencing a stringfied referent
by clueless newbie (Curate) on Jun 12, 2010 at 16:33 UTC
    This kind of gets me what I'm after without actually dereferencing the stringified referent. The replacement format_arg is "stashing" the stringified data structure while returning its stringified referent 
    #!

use Carp::Heavy;
use Data::Dumper;
use Scalar::Util;
use strict;
use warnings;

my @stash;
BEGIN {
    # Now redefine Carp::format_arg so we can dump refs too!
    no warnings qw(once redefine);
    *Carp::format_arg = sub { # shameless stolen from b. d foy
        package Carp;
        my $arg_s=shift;

        my $return_s;
        if (not defined $arg_s) {
            $return_s='undef';
             }
        elsif (Scalar::Util::blessed($arg_s)) { # an object
            $return_s="'".ref($arg_s)."(object/class)'";
             }
        elsif (ref($arg_s)) { # a ref
            require Data::Dumper;
            local $Data::Dumper::Indent=0;
            local $Data::Dumper::Terse=0;
            # deparse CodeRefs
            local $Data::Dumper::Deparse=ref($arg_s) eq 'CODE';
            $return_s=Data::Dumper::Dumper($arg_s);
            $return_s=~ s/^\$VAR\d+\s*=\s*//;
            $return_s=~ s/;\s*$//;
            $return_s=~ s/   */  /g
                if (ref($arg_s) eq 'CODE');
            push(@stash,$return_s);
            $return_s="'$arg_s($#stash)'";
             }
        else {
            $return_s=$arg_s;
            $return_s=~ s/'/\\'/g;
            $return_s=str_len_trim($arg_s,$Carp::Heavy::MaxArgLen);
            $return_s="'$arg_s'" unless $arg_s =~ /^-?[\d.]+\z/;
             }
        $return_s=~ s/([[:cntrl:]]|[[:^ascii:]])/sprintf("\\x{%x}",ord
+($1))/eg;
        return $return_s;
         };
     }; # BEGIN:

$SIG{__WARN__}=sub {
    my $buffer=Carp::longmess();
    print STDOUT "$buffer\n";
    print STDOUT "$_: $stash[$_]\n" for (0..$#stash);
    @stash=();
     };

# Just some code to test
use CGI;
my $q=CGI->new();
main(1,[2],{3=>$q},sub { return "huh" },$q);

sub main {
    warn "main";
    shift; shift;
    subroutine(@_);
     };

sub subroutine {
    warn "sub";
    die "just for fun!";
     };

    [download]
    It yields:
     
 at Dump.pl line 62
        main::main(1, 'ARRAY(0x1bba4ec)(0)', 'HASH(0x1b58b5c)(1)', 'CO
+DE(0x1a6d4a4)(2)', 'CGI(object/class)') called at Dump.pl line 59

0: [2]
1: {'3' => bless( {'.parameters' => [],'use_tempfile' => 1,'.charset' 
+=> 'ISO-8859-1','.fieldnames' => {},'param' => {},'escape' => 1}, 'CG
+I' )}
2: sub {  use warnings;  use strict 'refs';  return 'huh';}
 at Dump.pl line 68
        main::subroutine('HASH(0x1b58b5c)(0)', 'CODE(0x1a6d4a4)(1)', '
+CGI(object/class)') called at Dump.pl line 64
        main::main(1, 'ARRAY(0x1bba4ec)(2)', 'HASH(0x1b58b5c)(3)', 'CO
+DE(0x1a6d4a4)(4)', 'CGI(object/class)') called at Dump.pl line 59

0: {'3' => bless( {'.parameters' => [],'use_tempfile' => 1,'.charset' 
+=> 'ISO-8859-1','.fieldnames' => {},'param' => {},'escape' => 1}, 'CG
+I' )}
1: sub {  use warnings;  use strict 'refs';  return 'huh';}
2: [2]
3: {'3' => bless( {'.parameters' => [],'use_tempfile' => 1,'.charset' 
+=> 'ISO-8859-1','.fieldnames' => {},'param' => {},'escape' => 1}, 'CG
+I' )}
4: sub {  use warnings;  use strict 'refs';  return 'huh';}
just for fun! at Dump.pl line 69.

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