Topics:

1. Evolution of event-driven programming:
X Wait for a key press or line of text.
X Interrupts (hardware and software).
X Modern event loops

2. Types of events in modern applications:
X IO
X Timer
X User input
X Signal
X Anything that can spontaneously happen in the real world.

3. How to write a modern event-loop.
X kernel facilities (poll, select, etc.)

4. List of already-built event loops.
- EV
- Glib

5. Event-driven programming in Perl
- POE
- AnyEvent
- IO::Async
- Mojo::IOLoop

6. Special considerations
- Exceptions in event-driven code.
- SIGPIPE, EPIPE - might have more to do with long-lived processes rather than
  just event-driven programming, but still something to watch out for...

7. Promises:
- Future
- Future::AsyncAwait
- Future::Utils

8. Real-world uses for event-driven applications:
- Webhooks
- PubsubHubbub
- msg queue




Other topics:
X What is event-driven programming?
- Reactor: event loop that can receive multiple types of events and
  demultiplex them, delivering them to appropriate handlers.
- C10k problem
- EDA (event-driven architecture)
- Benefits of Event-driven

Traditional programs:
- CGI - web server calls your program, and your program does its thing and
  finishes.
- filters - grep, less, sed, etc. Like a function, the program takes its input
  and produces some output.

Perl features:
- first-class subroutines

- Can mix traditional architecture with event-driven (like docker that
  provides both an http and command-line interface.