How can you use look in a verb?

The Word look is a verb and can be used in many ways. Some examples:

present simple - The customs officers look in everybody's bag. She looks worried

past simple - They looked in my bag. John lookedsick

present continuous - I am looking for my dog. He is looking tired.

past continuous - She was looking for her dog. They were looking worried

present perfect - They have looked for the boy all day.

past perfect - I had looked at the book before.