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Hash::Case::Preserve - hash with enforced lower cased keys


   is a Hash::Case
   is a Tie::StdHash


 use Hash::Case::Preserve;
 tie my(%cphash), 'Hash::Case::Preserve';
 $cphash{StraNGeKeY} = 3;
 print keys %cphash;         # StraNGeKeY
 print $cphash{strangekey};  # 3
 print $cphash{STRANGEKEY};  # 3


Hash::Case::Preserve extends Hash::Case, which lets you play various trics with hash keys. This extension implements a fake hash which is case-insentive. The keys are administered in the casing as they were used: case-insensitive but case-preserving.

Extends "DESCRIPTION" in Hash::Case.


Extends "METHODS" in Hash::Case.


Extends "Constructors" in Hash::Case.


Inherited, see "Constructors" in Hash::Case


Inherited, see "Constructors" in Hash::Case


Inherited, see "Constructors" in Hash::Case

tie(HASH, 'Hash::Case::Preserve', [VALUES,] OPTIONS)

Define HASH to be case insensitive, but case preserving. The hash is initialized with the VALUES, specified as ref-array (passing a list of key-value pairs) or ref-hash.

OPTIONS is a list of key/value pairs, which specify how the hash must handle preservation. Current options:

  keep    'LAST'
keep => 'FIRST' | 'LAST'

Which casing is the preferred casing? The FIRST appearance or the LAST. Only stores will affect the casing, deletes will undo the definition. Defaults to LAST, which is slightly faster.


This module is part of Hash-Case distribution version 1.05, built on February 06, 2020. Website:


Copyrights 2002-2020 by [Mark Overmeer <>]. For other contributors see ChangeLog.

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