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Clone::PP(3) User Contributed Perl Documentation Clone::PP(3)


Clone::PP - Recursively copy Perl datatypes


  use Clone::PP qw(clone);
  $item = { 'foo' => 'bar', 'move' => [ 'zig', 'zag' ]  };
  $copy = clone( $item );
  $item = [ 'alpha', 'beta', { 'gamma' => 'vlissides' } ];
  $copy = clone( $item );
  $item = Foo->new();
  $copy = clone( $item );

Or as an object method:

  require Clone::PP;
  push @Foo::ISA, 'Clone::PP';
  $item = Foo->new();
  $copy = $item->clone();


This module provides a general-purpose clone function to make deep copies of Perl data structures. It calls itself recursively to copy nested hash, array, scalar and reference types, including tied variables and objects.

The clone() function takes a scalar argument to copy. To duplicate arrays or hashes, pass them in by reference:

  my $copy = clone(\@array);    my @copy = @{ clone(\@array) };
  my $copy = clone(\%hash);     my %copy = %{ clone(\%hash) };

The clone() function also accepts an optional second parameter that can be used to limit the depth of the copy. If you pass a limit of 0, clone will return the same value you supplied; for a limit of 1, a shallow copy is constructed; for a limit of 2, two layers of copying are done, and so on.

  my $shallow_copy = clone( $item, 1 );

To allow objects to intervene in the way they are copied, the clone() function checks for a couple of optional methods. If an object provides a method named "clone_self", it is called and the result returned without further processing. Alternately, if an object provides a method named "clone_init", it is called on the copied object before it is returned.


Some data types, such as globs, regexes, and code refs, are always copied shallowly.

References to hash elements are not properly duplicated. (This is why two tests in t/dclone.t that are marked "todo".) For example, the following test should succeed but does not:

  my $hash = { foo => 1 }; 
  $hash->{bar} = \{ $hash->{foo} }; 
  my $copy = clone( \%hash ); 
  $hash->{foo} = 2; 
  $copy->{foo} = 2; 
  ok( $hash->{bar} == $copy->{bar} );

To report bugs via the CPAN web tracking system, go to "" or send mail to "", replacing "#" with "@".


Clone - a baseclass which provides a clone() method.

MooseX::Clone - find-grained cloning for Moose objects.

The dclone() function in Storable.

Data::Clone - polymorphic data cloning (see its documentation for what that means).

Clone::Any - use whichever of the cloning methods is available.




Developed by Matthew Simon Cavalletto at Evolution Softworks. More free Perl software is available at "".


Copyright 2003 Matthew Simon Cavalletto. You may contact the author directly at "" or "".

Code initially derived from Portions Copyright 1994 David Muir Sharnoff.

Interface based by Clone by Ray Finch with contributions from chocolateboy. Portions Copyright 2001 Ray Finch. Portions Copyright 2001 chocolateboy.

You may use, modify, and distribute this software under the same terms as Perl.

2020-10-21 perl v5.40.0