$ perl -MHTML::Entities -e 'warn HTML::Entities::encode_entities("\x{20ac}")'
€ at -e line 1.
$ perl5.8.8 -MHTML::Entities -e 'binmode STDOUT, ":utf8"; print HTML::Entities::decode_entities("€"), "\n"'
(Drei Bytes für das utf-8-Zeichen)