Eventloop(3p)

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.