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Clone(3pm) User Contributed Perl Documentation Clone(3pm)


Clone - recursively copy Perl datatypes


    use Clone 'clone';
    my $data = {
       set => [ 1 .. 50 ],
       foo => {
           answer => 42,
           object => SomeObject->new,
    my $cloned_data = clone($data);
    $cloned_data->{foo}{answer} = 1;
    print $cloned_data->{foo}{answer};  # '1'
    print $data->{foo}{answer};         # '42'

You can also add it to your class:

    package Foo;
    use parent 'Clone';
    sub new { bless {}, shift }
    package main;
    my $obj = Foo->new;
    my $copy = $obj->clone;


This module provides a "clone()" method which makes recursive copies of nested hash, array, scalar and reference types, including tied variables and objects.

"clone()" takes a scalar argument and duplicates it. To duplicate lists, arrays or hashes, pass them in by reference, e.g.

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


Storable's "dclone()" is a flexible solution for cloning variables, albeit slower for average-sized data structures. Simple and naive benchmarks show that Clone is faster for data structures with 3 or fewer levels, while "dclone()" can be faster for structures 4 or more levels deep.


Copyright 2001-2019 Ray Finch. All Rights Reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.


Ray Finch "<>"

Breno G. de Oliveira "<>" and Florian Ragwitz "<>" perform routine maintenance releases since 2012.

2020-11-09 perl v5.32.0