Coding challenge: bad word filter

This is the first of our weekly coding challenges. Once a week we'll post a simple programming problem and the person who posts the best answer wins a T-shirt. The winner is decided by votes, or be comments, or be the audacity of their answer. Use any language in your answer except profanity.

Imagine that you allow users of your website to post comments, but some users, mainly the Australians, get a little colourful with their language. You decided to implement a Bad Word Filter that will replace certain words in a sentence with safer versions of that word.

The list of bad words and their replacements is

Bad: "poophead", "PHB", "gotten"
Replacement: "p**phead", "boss", "become"

So "My PHB is such a poophead. It's gotten worse since his promotion" should be "My boss is such a p**phead. It's become worse since his promotion".

We also have to allow shouting. So

"My PHB is such a POOPHEAD!" should become "My boss is such a P**PHEAD!"

Bonus points:

Let's make it harder. If the "bad" word starts with "*" then it means any word that ends with that word. If it ends with a star then any word starting with that. If it ends with an "!" then it means that it should do the match case sensitive.

Bad words: "poop*", "PHB!", "gotten"
Replacement: "p**p", "boss", "become"

"My PHB has started his new blog phblog.com. He's SUCH A MISBEGOTTEN POOPHEAD!"

should become

"My boss has started his new blog phblog.com. He's SUCH A MISBEGOTTEN P**PHEAD!"

What I have tried:

Remember: any programming language can be used.

Tags: Code challenge