use HTML::Entities;
use HTML::Entities qw( %char2entity %entity2char ); #thanks ikegami

foreach $val (keys %char2entity) {
	print "<br>$val => $char2entity{$val}\n";
}

$string = "this is an @ AT";
$string_2 = "é â ä à å ç ê ë è ï î ì Ä å É æ Æ ô ö ò û ù ÿ Ö Ü £ ¥ P ƒ á í ó ú ñ Ñ ª º ¿ ¬ ¬ ½ ¼ ¡ @ . , < > [ ] { } - _ ; :";
print "<p>encoded @ => ".encode_entities('@').", <br>and the string has become => ".encode_entities($string)." <br>and the string_2 has become => ".encode_entities($string_2)."\n";