http://www.perlmonks.org?node_id=1188207


in reply to Re^4: erroneous warning involving locale and input encoding: perl bug?
in thread erroneous warning involving locale and input encoding: perl bug?

The fault can be reduced to the following: 
use experimental 'smartmatch';
use POSIX 'locale_h';
use locale ':ctype';
setlocale(LC_CTYPE, 'en_US');

$_ = "x";
utf8::upgrade($_);
/x(y|z)?/;

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which gives an assert failure on bleadperl. The locale-variant of the TRIE code in the regex engine appears to be treating the 'no more chars' special value of nextchr (-10) as a real large utf8 character: 
                        && UTF8_IS_ABOVE_LATIN1(nextchr)

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By all means perlbug it

Dave.

In Section Seekers of Perl Wisdom