artist has asked for the wisdom of the Perl Monks concerning the following question:

There is a Firefox extension, WebDeveloper. It has one menu item, outline current element. It shows position of element. Example:
"html > body #id-479 > center > table > tbody > tr > td .main_content > form > table > tbody > tr > td > ul" 
for an element in this page. Now, I like to write this type of information into a file, when I highlight an element on the web browser. I like to do this with Perl. Where should I begin?