sub loop
{
  my $self = shift;
  my $heartbeat = shift;
  $self->{_endloop} = 0;

  while (!$self->{_endloop} && keys %{$self->{_fhs}}) {
    foreach my $k (keys %{$self->{_handles}}) {
      [...]
      # Is this descriptor ready for reading?
      if (fd_isset($rdready, $fh))
      {
        if ($self->{_fhs}{"$fh"}{listen}) {
          # It's a server socket, so a new connection is
          [...]
        } else {
          if ($self->is_udp($fh)) {
            [...]
          } else {
            $rv = &POSIX::read(fileno($fh), $data, BUFSIZ);
          }
          [...]
        }
      }  # end if readable
      next unless exists $self->{_fhs}{"$fh"};

      if (fd_isset($wrready, $fh)) {
        unless (length $self->{_fhs}{"$fh"}{outbuffer}) {
          [...]
        }
        $rv = &POSIX::write(fileno($fh),
                            $self->{_fhs}{"$fh"}{outbuffer},
                            length($self->{_fhs}{"$fh"}{outbuffer}));
          [...]
      }  # End if writeable
      next unless exists $self->{_fhs}{"$fh"};

    }  # End foreach $fh (...)

    $self->_checkTimeouts() if @{$self->{_timers}};

  } # End while(loop)
}

##</code><code>##

package IO::Multiplex;
[...]
sub add {
   [...]
   $self->{_fhs}{"$fh"}{writefun} = $fh->can('syswrite');
   $self->{_fhs}{"$fh"}{readfun} = $fh->can('sysread');
   [...]
}