In order to make \U work with accented chars I had to start my program like this:

$loc = 'pt_PT.ISO_8859-1';  # my locale
$ENV{'LANG'} = $loc;
$ENV{'LC_ALL'} = $loc;
$ENV{'LOCPATH'} = '/usr/share/locale';
use locale;
require POSIX;
POSIX::setlocale(&POSIX::LC_ALL, $loc);
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Is there a shorter way?