Issue #11284 has been reported by Pablo Herrero.

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Bug #11284: String#upcase and String#downcase don't work for accented characters
https://bugs.ruby-lang.org/issues/11284

* Author: Pablo Herrero
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-linux]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
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Many accented and other non-english characters fails to upcase/downcase properly.
Accented characters is the most common are the ones I keep stumbling upon,,but probably other germanic/nordic characters I'm not aware of have the same problems.

For example:

    "Hola, Cmo ests?".upcase         # returns "HOLA, CMO ESTS?"
    "CONFIANA".downcase                # returns "confiana"
    "Un moment s'il vous plat".upcase  # returns "UN MOMENT S'IL VOUSPLAT"



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