Why does this combo of Data::Dumper and Clone::clone() fail? Bug?

Lightknight has asked for the wisdom of the Perl Monks concerning the following question:

I didn't expect these results of using Data::Dumper (with Useperl(1)) and Clone::clone together. This snippet:

#!/usr/bin/perl -w
use strict;
use Clone;
use Data::Dumper;

printf "Clone: %s Data::Dumper %s\n",
    $Clone::VERSION,
    $Data::Dumper::VERSION;

my $orig = {
    # This could be arbitrariliy complicated/nested 
    # - this suffices for a demo
    # of the probem
    'array' => [ 1,2,3 ]
};

# Put it throught Data::Dumper with Userperl(1);
my $d = Data::Dumper->new([$orig]);
$d->Useperl(1);
$d->Dump();

# Make a clone - it should be identical, I guess
my $clone = Clone::clone($orig);

# See that the clone has a different structure in array
# (length of $$clone{array} is 0)
printf "orig: %d clone %d\n",
    scalar(@{$$orig{array}}),
    scalar(@{$$clone{array}});
[download]

Produces this output:

Clone: 0.29 Data::Dumper 2.121_14
orig: 3 clone 0
[download]

I would have expected

Clone: 0.29 Data::Dumper 2.121_14
orig: 3 clone 3
[download]

Since the orig and the clone should have been identical. Right? Is there a bug here? Where?

Comment on Why does this combo of Data::Dumper and Clone::clone() fail? Bug? Select or Download Code

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Re: Why does this combo of Data::Dumper and Clone::clone() fail? Bug? by ikegami (Patriarch) on Dec 16, 2010 at 20:46 UTC
In some version of Perl, Data::Dumper inadvertently adds "@" magic to the arrays it dumps. That magic has been supported since Clone 0.30. It was originally reported here. Simplest test case: `#!/usr/bin/perl -w use strict; use Clone; use Test::More tests => 1; diag("Clone " . $Clone::VERSION); my $orig = [ 1,2,3 ]; my $r = \$#$orig; # Add "@" magic to @$orig. my $clone = Clone::clone($orig); is(0+@$clone, 0+@$orig); 1;` [download] `1..1 # Clone 0.29 not ok 1 # Failed test at a.pl line 9. # got: '0' # expected: '3' # Looks like you failed 1 test of 1.` [download] `1..1 # Clone 0.31 ok 1` [download] Upgrade Clone to 0.30 or higher.	[reply] [d/l] [select]
Re: Why does this combo of Data::Dumper and Clone::clone() fail? Bug? by BrowserUk (Patriarch) on Dec 16, 2010 at 18:56 UTC
FWIW: I get your expected results. Albeit from slightly later versions of both modules: `C:\test>junk11 Clone: 0.31 Data::Dumper 2.125 orig: 3 clone 3` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l]