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```{index} single: clone; Digest::SHA function
```
```{index} single: Digest::SHA::clone; Perl function
```

# clone

Copy a `Digest::SHA` object, producing an independent duplicate.

Returns a new object with the same algorithm and the same internal state
— including any data already absorbed via `add` or `addfile`. The copy
and the original are independent from that moment on: hashing more data
into one does not affect the other.

Useful when you want several digests that share a common prefix, for
example hashing a large buffer followed by a per-record suffix.

## Synopsis

```perl
my $base = Digest::SHA->new(256);
$base->add($prefix);
my $copy = $base->clone;
```

## What you get back

A fresh blessed `Digest::SHA` object with state copied from the receiver.
Returns `undef` if called on something that is not a valid
`Digest::SHA` object.

## Examples

```perl
my $base = Digest::SHA->new(256);
$base->add("common-prefix:");
for my $id (1 .. 3) {
    my $h = $base->clone;
    $h->add($id);
    print $h->hexdigest, "\n";   # three distinct digests
}
```

```perl
my $sha = Digest::SHA->new(512);
$sha->add("abc");
my $copy = $sha->clone;
print $copy->hexdigest eq $sha->hexdigest ? "same\n" : "diff\n"; # same
```

## Edge cases

- The copy is a snapshot: subsequent `add` on the receiver does not
  propagate into it.
- `clone` on a non-`Digest::SHA` scalar returns `undef` rather than
  croaking.

## Differences from upstream

Fully compatible with upstream `Digest::SHA` {{ upstream.Digest_SHA }}.

## See also

- `new` — start a fresh context instead of branching from an existing one.
- `reset` — reuse the same object for the next digest.
- `getstate` / `putstate` — snapshot to a string you can send across processes.