Help wanted with plugin that changes content etc when post saved

Can someone get me started on the following – maybe pointing me in the direction of a similar type of example that I can start with.

What I want to do is, at the time I save a post (before it actually gets into the database) is:

Read the content of the post and find any occurrence of [title New Post Title] and save and remove it.

I then want to use New Post Title as the post title.

For example, the content of the post might be:

“[title Dummy Post]
<p>This is a dummy post.</p>”

The result should be a post with title “Dummy Post” and content “<p>This is a dummy post.</p>”

I have written a couple of simple plugins (just for myself) before but they’ve been based on going through the content when a post is displayed, not saved.