Use case for utf8::upgrade?

[email protected] (Michael Ludwig) Wed, 7 Apr 2010 14:41:25 +0200

Newsgroups	perl.unicode
Message-ID	<[email protected]>

Perl Unicode Advice
http://juerd.nl/site.plp/perluniadvice

Having read Juerd's list of useful advice, I don't understand the reason for its last three items:

• utf8::upgrade before doing lc/lcfirst/uc
• utf8::upgrade before doing case insensitive matching
• utf8::upgrade before matching predefined character classes like w and s

Can anyone enlighten me on the background of using utf8::upgrade here?
-- 
Michael.Ludwig (#) XING.com