my @data = (1,2,3,4);

my $existing_ref = \@data;
my $new_ref = [@data];

$existing_ref->[0] = "a";
$new_ref->[2] = "c";

Now, @data contains
(a,2,3,4) 

and $new_ref points to an array the contains
(1,2,c,4)