NAME
    Hash::Subset - Produce subset of a hash

VERSION
    This document describes version 0.002 of Hash::Subset (from Perl
    distribution Hash-Subset), released on 2019-07-10.

SYNOPSIS
     use Hash::Subset qw(hash_subset hashref_subset);

     # using keys specified in an array
     my %subset = hash_subset   ({a=>1, b=>2, c=>3}, ['b','c','d']); # => (b=>2, c=>3)
     my $subset = hashref_subset({a=>1, b=>2, c=>3}, ['b','c','d']); # => {b=>2, c=>3}

     # using keys specified in another hash
     my %subset = hash_subset   ({a=>1, b=>2, c=>3}, {b=>20, c=>30, d=>40}); # => (b=>2, c=>3)
     my $subset = hashref_subset({a=>1, b=>2, c=>3}, {b=>20, c=>30, d=>40}); # => {b=>2, c=>3}

DESCRIPTION
FUNCTIONS
    None exported by default.

  hash_subset
    Usage:

     my %subset  = hash_subset   (\%hash, \@keys);
     my $subset  = hashref_subset(\%hash, \@keys);
     my %subset  = hash_subset   (\%hash, \%another_hash);
     my $subset  = hashref_subset(\%hash, \%another_hash);

    Produce subset of %hash, returning the subset hash (or hashref, in the
    case of "hashref_subset" function).

    Perl lets you produce a hashref using the slice notation:

     my %subset = %hash{"b","c","d"};

    The difference with this routine is: 1) hash slice is only available
    since perl 5.20 (in previous versions, only array slices is available);
    2) when the key does not exist in the array, perl will create it for you
    with "undef" as the value, so:

     my %hash   = (a=>1, b=>2, c=>3);
     my %subset = %hash{"b","c","d"}; # => (b=>2, c=>3, d=>undef)

    So basically "hash_subset" is equivalent to:

     my %subset = %hash{grep {exists $hash{$_}} "b","c","d"}; # => (b=>2, c=>3, d=>undef)

    and available for perl earlier than 5.20.

  hashref_subset
    See "hash_subset".

HOMEPAGE
    Please visit the project's homepage at
    <https://metacpan.org/release/Hash-Subset>.

SOURCE
    Source repository is at <https://github.com/perlancar/perl-Hash-Subset>.

BUGS
    Please report any bugs or feature requests on the bugtracker website
    <https://rt.cpan.org/Public/Dist/Display.html?Name=Hash-Subset>

    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
    Some other hash utilities: Hash::MostUtils

AUTHOR
    perlancar <perlancar@cpan.org>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2019 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.