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

##</code><code>##

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];

##</code><code>##

use Data::Dumper;
use Storable qw/dclone/;

my @a = (1,2,3,4,6);
$Data::Dumper::Indent=0;
print Dumper(increment(increment(\@a))), "\n";

sub increment{
   my $d = shift;
   my @b;
   for my $i (1..$#$d){
      my @a = @$d[$i-1..$i];
      push @b, dclone \@a;
   }
   return \@b;
}

__END__

$VAR1 = [[[1,2],[2,3]],[[2,3],[3,4]],[[3,4],[4,6]]];

##</code><code>##

use Data::Dump;
my $aref = ['x','y'];
my @a = ($aref, $aref);
dd \@a;
__END__
do {
  my $a = [["x", "y"], 'fix'];
  $a->[1] = $a->[0];
  $a;
}

##</code><code>##

use Data::Dumper;
$Data::Dumper::Deepcopy = 1;
$Data::Dumper::Indent = 0;
my $aref = ['x','y'];
my @a = ($aref, $aref);
print Dumper(\@a), "\n";
__END__
$VAR1 = [['x','y'],['x','y']];