my $pipe;
eval {
	local $SIG{ALRM} = sub { die "alarm\n" };
	alarm(5);
	open( $pipe, "<", $pipe_path )
		or die "pipe open failed: $!";
	alarm(0);
};
if ($@) {
	die unless ($@ eq "alarm\n"); # non-alarm failure.
	die "timeout on pipe open";
}

##</code><code>##

use strict;
use warnings;
require IO::Select;	# OO interface to select(2) & friends.
require IO::Handle;	# treat handles as objects.
require POSIX;		# supplies access to errno E* values

sub debug{ printf STDERR "%s\n", shift // ''; }

my $pipe_path = "pipe";	# you must mkfifo this file first!

debug("opening pipe");
open( my $pipe, "<", $pipe_path )
	or die "pipe open failed: $!";
debug("pipe opened");

$pipe->blocking(0);	# set non-blocking on the descriptor

my $s = IO::Select->new();
$s->add($pipe);

# Holds unbuffered chars read. We only want full lines:
my $buf = "";

# Inefficient polling loop. Nonblocking because we're "busy".
POLL:
while (1) {
	# Nothing to do unless the FD reports ready.
	# When there's no data, the 'continue' block is run.
	next POLL unless ( my @ready = $s->can_read(.25) );

	# This is really slow. Smarter would be to read in chunks,
	# then search for a newline. If we have none, append to buffer.
	# We take the slow approach for this example & read just 1 char.
	my $bytes = $pipe->sysread( $buf, 1, length($buf) );
	
	# You MUST test for errors using sysread. See docs, and read(2).
	# In this case, we also must verify we don't get EAGAIN.
	# In rare cases, select(2) indicates a possible read when there's not.
	if (not defined $bytes) {
		next POLL if ($! == POSIX->EAGAIN);
		# Error: report $! (errno) and exit
		debug("An error occurred on read: $!");
		exit(1);
	}

	# $bytes == 0 means EOF. Nothing more to read.
	if ($bytes == 0) {
		print "Reached EOF. All done reading from pipe.\n";
		close($pipe);	# no point in checking for errors here.
		exit(0);
	}

	# Otherwise, check the character just read. Print/reset on newlines:
	if ( substr($buf, -1) eq "\n" ) {
		print "Pipe line read: $buf";
		$buf = "";
	}
}
continue {
	# Your idle work when there's nothing to do happens here.
	# This silly example just prints a period each poll interval.
	print STDERR ".";
}

##</code><code>##

use strict;
use warnings;
require IO::Handle;

my $pipe_path = "pipe";

open( my $pipe, ">", $pipe_path )
	or die "pipe open failed: $!";

$pipe->autoflush(1);

while( my $line = <> ) {
	chomp $line;
	print $pipe $line . "\n";
}

close($pipe)
	or die "Closing pipe failed: $!";