6 D: Start or resume playing.
8 H: Without <num>, starts playing at the current position. Otherwise, the
9 H: corresponding file is loaded and playback is started.
14 H: When paused, it is still possible to jump around in the file via the jmp and ff
18 D: Print list of active tasks.
20 H: Mainly useful for debugging.
25 H: Pressing CTRL+D causes EOF on stdin which also exits para_play.