No, thanks, it was a silly typo mistake... :) It works ok now, but the problem remains with the authors...
In particular, the above code (which I created based on your help) works fine when I have more than one author. But, if I have only one, it says :  Not an ARRAY reference at read_xml.pl line 19 (line 19 is the foreach loop).
So, I was wondering, is there a way of finding out if I have one or more authors in my xml entry? Thank you all for your time!