use locale;
use POSIX qw (locale_h);
setlocale(LC_CTYPE, 'Russian_Russia.1251');
print lc ('ПРИВЕТ'); 

##</code><code>##

$s = "&#1055;&#1056;&#1048;&#1042;&#1045;&#1058;";
$s =~ tr/\xA8\xC0-\xDF/\xB8\xE0-\xFF/; # lc RusCyr Win1251
print $s;