IO::Event provides a object-based callback system for handling nonblocking
IO. The design goal is to provide a system that just does the right thing
w/o the user needing to think about it much.

All APIs are kept as simple as possible yet at the same time, all
functionality is accesible if needed. Simple things are easy. Hard things
are possible.

Most of the time file handling syntax will work fine: <$filehandle> and
print $filehandle 'stuff'.

IO::Event provides automatic buffering of output (with a callback to
throttle). It provides automatic line-at-a-time input.

After initial setup, call IO::Event::loop().

IO::Event was originally written to use Event. IO::Event still defaults to
using Event but it can now use AnyEvent or its own event loop.