Well, following Starsons advice in another thread [use regexp to get info from the file name], I'm close to get the authors listed by <last-name, first-name>.
I found that the default regexp, found in the "Preferences ->Adding Books" menu is almost what I need.
Code:
(?P<title>.+) - (?P<author>[^_]+)
Thus, for a file named "SuchandSuch - Azimov_Isaac.epub" I got title="SuchandSuch", author="Asimov Isaac".
However, I would like to get author="Asimov, Isaac". Now, AFAIK regexps are for pattern matching, not for string processing. So, my question is if there is a way to get that extra comma between the last name and the first name.