51873 Easy PHP or CGI script

Hello, I need a script that will modify a couple of hundred .shtml web pages. The pages are all in one folder on my server. I want you to create a script that will let me add a piece of code to each page. It needs to read each page and find the /body tag and then insert my java script code just above that line. Then save. That's it. I hope this is relatively easy and I can help some new programmer get some good feedback. Thanks, David