Hash::Case(3)

NAME
Hash::Case - base class for hashes with key-casing requirements

INHERITANCE
 Hash::Case
   is a Tie::StdHash

 Hash::Case is extended by
   Hash::Case::Lower
   Hash::Case::Preserve
   Hash::Case::Upper

SYNOPSIS
  use Hash::Case::Lower;
  tie my(%lchash), 'Hash::Case::Lower';
  $lchash{StraNGeKeY} = 3;
  print keys %lchash;  # strangekey

  (tied %lchash)->addPairs(key => value, ...);
  (tied %lchash)->addHashData(\%data);
  (tied %lchash)->setHash(\%replacement);

DESCRIPTION
Hash::Case is the base class for various classes which tie special treatment for the casing of keys. Be aware of the differences in implementation: "Lower" and "Upper" are tied native hashes: these hashes have no need for hidden fields or other assisting data structured. A case "Preserve" hash will actually create three hashes.

The following strategies are implemented:

•   Hash::Case::Lower (native hash)

    Keys are always considered lower case. The internals of this module translate any incoming key to lower case before it is used.

•   Hash::Case::Upper (native hash)

    Like the ::Lower, but then all keys are always translated into upper case. This module can be of use for some databases, which do translate everything to capitals as well. To avoid confusion, you may want to have you own internal Perl hash do this as well.

•   Hash::Case::Preserve

    The actual casing is ignored, but not forgotten.

METHODS

  Constructors

tie %hash, $class, [$values,] %options
    Tie the %hash with the $class (package which extends Hash::Case). The %options differ per implementation: read the manual page for the package you actually use. The optional $values is a reference to an ARRAY (containing key-value PAIRS) or a HASH: they fill-in the initial %hash.

    » example:

      my %x;
      tie %x, 'Hash::Case::Lower';
      $x{Upper} = 3;
      print keys %x;       # 'upper'

      my @y = (ABC => 3, DeF => 4);
      tie %x, 'Hash::Case::Lower', \@y;
      print keys %x;       # 'abc' 'def'

      my %z = (ABC => 3, DeF => 4);
      tie %x, 'Hash::Case::Lower', \%z;

  Hidden object access
Besides all the usual HASH actions which are implemented for the tied %hash, you can also call methods on the tied() object.

$obj->addHashData(\%data)
    Add the %data to the created tied hash. The existing values in the hash remain, the keys are adapted to the needs of the the casing.

$obj->addPairs(@pairs)
    Specify an even length list of alternating key and value to be stored in the hash.

$obj->setHash(\%data)
    The functionality differs for native and wrapper hashes. For native hashes, this is the same as first clearing the hash, and then a call to addHashData(). Wrapper hashes will use the hash you specify here to store the data, and re-create the mapping hash.

SEE ALSO
This module is part of Hash-Case version 1.07, built on January 26, 2026. Website: http://perl.overmeer.net/CPAN/

LICENSE
For contributors see file ChangeLog.

This software is copyright (c) 2002-2026 by Mark Overmeer.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.