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;
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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.
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1..1
# Clone 0.31
ok 1
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Upgrade Clone to 0.30 or higher.