Thank you, in turn, for reminding me of fc! It seems to me that for Cyrillic alphabet as it is used in Russian, fc and lc are equivalent: 
use v5.16;
use charnames ':full';
use List::Util 'all';
say all { fc eq lc } map chr,
 ord("\N{CYRILLIC CAPITAL LETTER A}")..ord("\N{CYRILLIC SMALL LETTER Y
+A}")
__END__
1

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In reply to Re^6: Problem getting Russian stopwords by Anonymous Monk
in thread Problem getting Russian stopwords by cormanaz

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