NAME Acme::CPANModules::HashUtilities - Modules that manipulate hashes VERSION This document describes version 0.002 of Acme::CPANModules::HashUtilities (from Perl distribution Acme-CPANModules-HashUtilities), released on 2020-03-01. DESCRIPTION Modules that manipulate hashes. Most of the time, you don't need modules to manipulate hashes; Perl's built-in facilities suffice. The modules below, however, are sometimes convenient. This list is organized by task. Creating an alias to another variable Hash::Util's "hv_store" allows you to store an alias to a variable in a hash instead of copying the value. This means, if you set a hash value, it will instead set the value of the aliased variable instead. Copying from Hash::Util's documentation: my $sv = 0; hv_store(%hash,$key,$sv) or die "Failed to alias!"; $hash{$key} = 1; print $sv; # prints 1 Getting internal information Aside from creating restricted hash, Hash::Util also provides routines to get information about hash internals, e.g. "hash_seed()", "hash_value()", "bucket_info()", "bucket_stats()", etc. Merging Merging hashes is usually as simple as: my %merged = (%hash1, %hash2, %hash3); but sometimes you want different merging behavior, particularly in case where the same key is found in more than one hash. See the various hash merging modules: Hash::Merge Data::ModeMerge Hash::Union Providing default value for non-existing keys Hash::WithDefault Restricting keys Perl through Hash::Util (a core module) allows you to restrict what keys can be set in a hash. This can be used to protect against typos and for simple validation. (For more complex validation, e.g. allowing patterns of valid keys and/or rejecting patterns of invalid keys, you can use the tie mechanism.) Reversing (inverting) Reversing a hash (where keys become values and values become keys) can be done using the builtin's "reverse" (which actually just reverse a list): %hash = (a=>1, b=>2); %reverse = reverse %hash; # => (2=>"b", 1=>"a") Since the new keys can contain duplicates, this can "destroy" some old keys: %hash = (a=>1, b=>1); %reverse = reverse %hash; # => sometimes (1=>"b"), sometimes (1=>"a") Hash::MoreUtil's "safe_reverse" allows you to specify a coderef that can decide whether to ignore overwriting, croak, or whatever else. Slicing (creating subset) Hash::MoreUtils's "slice_*" functions. Hash::Subset Hash::Util::Pick Tying The tie mechanism, although relatively slow, allows you to create various kinds of "magical" hash that does things whenever you get or set keys. INCLUDED MODULES * Hash::Util * Hash::Merge * Data::ModeMerge * Hash::Union * Hash::WithDefault * Hash::MoreUtil * Hash::MoreUtils * Hash::Subset * Hash::Util::Pick FAQ What are ways to use this module? Aside from reading it, you can install all the listed modules using cpanmodules: % cpanmodules ls-entries HashUtilities | cpanm -n or Acme::CM::Get: % perl -MAcme::CM::Get=HashUtilities -E'say $_->{module} for @{ $LIST->{entries} }' | cpanm -n This module also helps lcpan produce a more meaningful result for "lcpan related-mods" when it comes to finding related modules for the modules listed in this Acme::CPANModules module. HOMEPAGE Please visit the project's homepage at . SOURCE Source repository is at . BUGS Please report any bugs or feature requests on the bugtracker website When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature. SEE ALSO Acme::CPANModules - about the Acme::CPANModules namespace cpanmodules - CLI tool to let you browse/view the lists AUTHOR perlancar COPYRIGHT AND LICENSE This software is copyright (c) 2020 by perlancar@cpan.org. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.