Execution sequence of Ruby programs

1. Search for the begin statement first, and execute the statement if it is found; otherwise, execute ProgramThe first line

2. When it comes to function definitions, class definitions, and module definitions, these things are defined.

3. Run the statement that causes the program to exit, or exit the execution when it reaches the end of the file or when it encounters _ end _.

4. Before exiting execution, a typical end statement block or an exit hook statement registered by at_exit is executed. However, if you use exit! The exit result. The preceding two cases are not executed.