use Data::Dumper;
my $aref = ['x','y'];
my @a = ($aref, $aref);
$Data::Dumper::Purity=1;
print Dumper(\@a);
__END__
$VAR1 = [
          [
            'x',
            'y'
          ],
          []
        ];
$VAR1->[1] = $VAR1->[0];