Sequence of execution of Ruby programs _ruby topics

1. Search first and then execute, otherwise the first line of execution program

2. function definition, class definition, module definition execution, causing these things to be defined

3. The statement that causes the program to exit, or to the end of the file or encountered __end__ to exit the execution

4. A typical execution end statement block or an exit Hook statement registered by At_exit before exiting execution. But if the exit caused by exit!, the previous two cases do not execute