I have written a little script that does something similar. I started from HTML::Entities, but since I use UTF-8 for storing my documents, and that module supposes ISO-8859-1, it didn't work.

So I converted the hash from the module (chars to entity names) in UTF-8 using iconv, added a switch, and it now works. You can find it served from my PC (it's a DynDNS name, so sometimes may be off-line)