EVENTLOOP(1)

NAME
Tk::Event - ToolKit for Events

SYNOPSIS use Tk::Event;

 Tk::Event->fileevent(\*FH, 'readable' => callback);
 Tk::Event->lineavail(\*FH, callback);
 use Tk::Event::Signal qw(INT);
 $SIG{'INT'} = callback;
 use Tk::Event::process;
 Tk::Event->proc($pid, callback);
 QueueEvent(callback [, position])

DESCRIPTION
That is better than nothing but still hard to use. Most scripts want higher level result (a line, a "block" of data etc.)

So it has occured to me that we could use new-ish TIEHANDLE thus:

my $obj = tie SOMEHANDLE,Tk::Event::IO;

while (<SOMEHANDLE>)
 {
 }

Then the READLINE routine registers a callback and looks something like:

sub READLINE
 {
  my $obj = shift;
  Event->io(*$obj,'readable',sub { sysread(*$obj,${*$obj},1,length(${*$obj}) });
  my $pos;
  while (($pos = index(${*$obj},$/) < 0)
   {
    DoOneEvent();
   }
  Event->io(*$obj,'readable',''); # unregister
  $pos += length($/);
  my $result = substr(${*$obj},0,$pos);
  substr(${*$obj},0,$pos) = '';
  return $result;
 }

This is using the scalar part of the glob representing the _inner_ IO as a buffer in which to accumulate chars.