You'll be pleased to know that File::Find has already been written to take care of the hard part of what you're looking for, you just have to add in the code you've written to check each file for the content.

If you haven't written the code that searches each file for content, running the command perldoc -f grep will put you on the right track. Although there are better and newer ways to do it nowadays, that will at least get you started. If you'd like to move forward, post what work you've done.