But XML::Parser expects "&" to look like "&amp;", too! And "<" like "&lt;". The rest is up to you...

So, after you decoded the entities, make sure to reencode at least these two, again.

If your character set doesn't agree with the XML files' content-encoding (which is UTF-8 by default), it's best to replace the special characters by numerical entities, too. For example, it's very safe to replace "à" with "&#224;", for example. The character ordinal code is in Unicode, of which ISO-Latin-1 is a subset for the range 0-255.