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Jens Rehsack
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Hash::MoreUtils - Provide the stuff missing in Hash::Util


  use Hash::MoreUtils qw(slice slice_def slice_exists slice_grep


Similar to List::MoreUtils, Hash::MoreUtils contains trivial but commonly-used functionality for hashes.



Returns a hash containing the (key, value) pair for every key in LIST.

slice_def HASHREF[, LIST]

As slice, but only includes keys whose values are defined.

slice_exists HASHREF[, LIST]

As slice but only includes keys which exist in the hashref.

slice_grep BLOCK, HASHREF[, LIST]

As slice, with an arbitrary condition.

Unlike grep, the condition is not given aliases to elements of anything. Instead, %_ is set to the contents of the hashref, to avoid accidentally auto-vivifying when checking keys or values. Also, 'uninitialized' warnings are turned off in the enclosing scope.

hashsort [BLOCK,] HASHREF

  my @array_of_pairs  = hashsort \%hash;
  my @pairs_by_length = hashsort sub { length($a) <=> length($b) }, \%hash;

Returns the (key, value) pairs of the hash, sorted by some property of the keys. By default (if no sort block given), sorts the keys with cmp.

I'm not convinced this is useful yet. If you can think of some way it could be more so, please let me know.

safe_reverse [BLOCK,] HASHREF

  my %dup_rev = safe_reverse \%hash

  sub croak_dup {
      my ($k, $v, $r) = @_;
      exists( $r->{$v} ) and
        croak "Cannot safe reverse: $v would be mapped to both $k and $r->{$v}";
  my %easy_rev = save_reverse \&croak_dup, \%hash

Returns safely reversed hash (value, key pairs of original hash). If no BLOCK is given, following routine will be used:

  sub merge_dup {
      my ($k, $v, $r) = @_;
      return exists( $r->{$v} )
             ? ( ref($r->{$v}) ? [ @{$r->{$v}}, $k ] : [ $r->{$v}, $k ] )
             : $k;

The BLOCK will be called with 3 arguments:


The key from the ( key, value ) pair in the original hash


The value from the ( key, value ) pair in the original hash


Reference to the reversed hash (read-only)

The BLOCK is expected to return the value which will used for the resulting hash.


Hans Dieter Pearcey, <hdp@cpan.org> Jens Rehsack, <rehsack@cpan.org>


Please report any bugs or feature requests to bug-hash-moreutils@rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Hash-MoreUtils. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.


You can find documentation for this module with the perldoc command.

    perldoc Hash::MoreUtils

You can also look for information at:



Copyright 2005 Hans Dieter Pearcey, all rights reserved. Copyright 2010 Jens Rehsack

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See http://dev.perl.org/licenses/ for more information.