Win32::API->Import(
   'mydll',
   'BOOL SomeFunction(
      LPDWORD lpCount
   )',
);

##</code><code>##

my $nCount = 5;
SomeFunction($nCount);

##</code><code>##

SomeFunction(undef);

##</code><code>##

use strict;
use warnings;

use Win32::API     qw( );
use Win32API::File qw( GetOsFHandle INVALID_HANDLE_VALUE );
use Time::HiRes    qw( sleep );


use constant ERROR_BROKEN_PIPE => 109;


sub get_pv { unpack 'L!', pack 'P', $_[0] }


BEGIN {
   # BOOL WINAPI PeekNamedPipe(
   #    __in       HANDLE  hNamedPipe,
   #    __out_opt  LPVOID  lpBuffer,
   #    __in       DWORD   nBufferSize,
   #    __out_opt  LPDWORD lpBytesRead,
   #    __out_opt  LPDWORD lpTotalBytesAvail,
   #    __out_opt  LPDWORD lpBytesLeftThisMessage
   # )

   my $f = Win32::API->new('kernel32', 'PeekNamedPipe', 'LLLLLL', 'L')
      or die $^E;

   sub PeekNamedPipe {
      my $nBytesRead;
      my $nTotalBytesAvail;
      my $nBytesLeftThisMessage;

      $nBytesRead            = pack('L!', $_[3]) if defined $_[3];
      $nTotalBytesAvail      = pack('L!', $_[4]) if defined $_[4];
      $nBytesLeftThisMessage = pack('L!', $_[5]) if defined $_[5];

      my $rv = $f->Call(
         $_[0],
         get_pv($_[1]),
         $_[2],
         get_pv($nBytesRead),
         get_pv($nTotalBytesAvail),
         get_pv($nBytesLeftThisMessage),
      );
      
      $_[3] = unpack('L!', $nBytesRead           ) if defined $_[3];
      $_[4] = unpack('L!', $nTotalBytesAvail     ) if defined $_[4];
      $_[5] = unpack('L!', $nBytesLeftThisMessage) if defined $_[5];

      return $rv;      
   }
}


my $cmd = 'perl -le"$|++;print localtime().q[: some text] and sleep 1 for 1..10" |';

my $pid = open my $pipe, $cmd
   or die $!;


( my $pHandle = GetOsFHandle( $pipe ) ) != INVALID_HANDLE_VALUE
   or die $^E;

print("Handle: $pHandle\n");


my $buf = '';
for (;;) {
   my $avail = 0;
   if ( !PeekNamedPipe( $pHandle, undef, 0, undef, $avail, undef ) ) {
      last if $^E == ERROR_BROKEN_PIPE;
      die $^E;
   }

   print("Avail: $avail");
   print(" (+" . length($buf) . ")") if length($buf);
   print("\n");

   if ( $avail ) {
      sysread($pipe, $buf, $avail, length($buf) )
         or die $!;

      while ( $buf =~ s/^(.*)\n// ) {
         my $line = $1;
         ## Do stuff with $line
         print( "Got: $line\n" );
      }
   }
   else {
      print( "Zzzz\n" );
      sleep(0.500);
   }
}

##</code><code>##

Handle: 1980
Avail: 0
Zzzz
Avail: 37
Got: Tue Sep 30 19:23:32 2008: some text
Avail: 0
Zzzz
Avail: 0
Zzzz
Avail: 37
Got: Tue Sep 30 19:23:33 2008: some text
Avail: 0
Zzzz
Avail: 0
Zzzz
Avail: 37
Got: Tue Sep 30 19:23:34 2008: some text
Avail: 0
Zzzz
Avail: 0
Zzzz
Avail: 37
Got: Tue Sep 30 19:23:35 2008: some text
Avail: 0
Zzzz
Avail: 0
Zzzz
Avail: 37
Got: Tue Sep 30 19:23:36 2008: some text
Avail: 0
Zzzz
Avail: 0
Zzzz
Avail: 37
Got: Tue Sep 30 19:23:37 2008: some text
Avail: 0
Zzzz
Avail: 0
Zzzz
Avail: 37
Got: Tue Sep 30 19:23:38 2008: some text
Avail: 0
Zzzz
Avail: 0
Zzzz
Avail: 37
Got: Tue Sep 30 19:23:39 2008: some text
Avail: 0
Zzzz
Avail: 0
Zzzz
Avail: 37
Got: Tue Sep 30 19:23:40 2008: some text
Avail: 0
Zzzz
Avail: 0
Zzzz
Avail: 37
Got: Tue Sep 30 19:23:41 2008: some text
Avail: 0
Zzzz
Avail: 0
Zzzz