Sorry I haven't had enough time to input my experience in this field. I need to look for my code, put it here and explain it.
Nevertheless, this is a very commented topic. Please check the following links that may be helpful for you:
http://www.linuxjournal.com/content/reading-native-excel-files-perl
http://www.ibm.com/developerworks/linux/library/l-pexcel/
http://stackoverflow.com/questions/2134707/how-can-i-read-excel-files-in...