use HTML::Entities;

my $input = "abc < ä > <p> Ö & ü xyz ";  # ISO-Latin-1

my $encoded;

$encoded = encode_entities($input, "\xA0-\x{FFFD}");
print "$encoded\n";

# now upgrade $input to character string (utf8)
# (by appending some unicode characters)
$input .= "\x{5555} \x{8888}";

$encoded = encode_entities($input, "\xA0-\x{FFFD}");
print "$encoded\n";