my @first = ( ['1','2','3'],
           ['11','22','33'] );

my @second = map { reref ( @$_ ) } @first;
$first[0][2] = 4;

print "$first[0][2]\n";
print "$second[0][2]\n";

sub reref {
    my @out = ();
    push (@out, $_) for @_; 
    return \@out;
}