This collection of modules allows programs to be written that perform
asynchronous filehandle IO operations. A typical program using them would
consist of a single subclass of IO::Async::Set to act as a container for a
number of IO::Async::Notifier objects (or subclasses thereof). The set itself is
responsible for checking read- or write-readiness, and informing the notifiers
of these conditions. The notifiers then perform whatever work is required on
these conditions, by using subclass methods or callback functions.

WWW: http://search.cpan.org/dist/IO-Async/