=head1 NAME

AnyEvent - provide framework for multiple event loops

EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops

=head1 SYNOPSIS

   use AnyEvent;

   my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {
      ...
   });

   my $w = AnyEvent->timer (after => $seconds, cb => sub {
      ...
   });

   my $w = AnyEvent->condvar; # stores whether a condition was flagged
   $w->send; # wake up current and all future recv's
   $w->recv; # enters "main loop" till $condvar gets ->send

=head1 INTRODUCTION/TUTORIAL

This manpage is mainly a reference manual. If you are interested
in a tutorial or some gentle introduction, have a look at the
L<AnyEvent::Intro> manpage.

=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)

Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
nowadays. So what is different about AnyEvent?

Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
policy> and AnyEvent is I<small and efficient>.

First and foremost, I<AnyEvent is not an event model> itself, it only
interfaces to whatever event model the main program happens to use in a
pragmatic way. For event models and certain classes of immortals alike,
the statement "there can only be one" is a bitter reality: In general,
only one event loop can be active at the same time in a process. AnyEvent
helps hiding the differences between those event loops.

The goal of AnyEvent is to offer module authors the ability to do event
programming (waiting for I/O or timer events) without subscribing to a
religion, a way of living, and most importantly: without forcing your
module users into the same thing by forcing them to use the same event
model you use.

For modules like POE or IO::Async (which is a total misnomer as it is
actually doing all I/O I<synchronously>...), using them in your module is
like joining a cult: After you joined, you are dependent on them and you
cannot use anything else, as it is simply incompatible to everything that
isn't itself. What's worse, all the potential users of your module are
I<also> forced to use the same event loop you use.

AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
fine. AnyEvent + Tk works fine etc. etc. but none of these work together
with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
your module uses one of those, every user of your module has to use it,
too. But if your module uses AnyEvent, it works transparently with all
event models it supports (including stuff like POE and IO::Async, as long
as those use one of the supported event loops. It is trivial to add new
event loops to AnyEvent, too, so it is future-proof).

In addition to being free of having to use I<the one and only true event
model>, AnyEvent also is free of bloat and policy: with POE or similar
modules, you get an enormous amount of code and strict rules you have to
follow. AnyEvent, on the other hand, is lean and up to the point, by only
offering the functionality that is necessary, in as thin as a wrapper as
technically possible.

Of course, AnyEvent comes with a big (and fully optional!) toolbox
of useful functionality, such as an asynchronous DNS resolver, 100%
non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
such as Windows) and lots of real-world knowledge and workarounds for
platform bugs and differences.

Now, if you I<do want> lots of policy (this can arguably be somewhat
useful) and you want to force your users to use the one and only event
model, you should I<not> use this module.

=head1 DESCRIPTION

L<AnyEvent> provides an identical interface to multiple event loops. This
allows module authors to utilise an event loop without forcing module
users to use the same event loop (as only a single event loop can coexist
peacefully at any one time).

The interface itself is vaguely similar, but not identical to the L<Event>
module.

During the first call of any watcher-creation method, the module tries
to detect the currently loaded event loop by probing whether one of the
following modules is already loaded: L<EV>,
L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
L<POE>. The first one found is used. If none are found, the module tries
to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
adaptor should always succeed) in the order given. The first one that can
be successfully loaded will be used. If, after this, still none could be