Update In the code below the main difference with respect to johngg's version is the use of the straight pipe function instead of IO::Pipe. It turned out (thanks to johngg's tests) that using straight pipes allowed him to trap the PIPE signal, which he couldnt' using the module. I tried to peek into the module and found nothing about SIGPIPE trapping, but I didn't dig this up to the modules included by IO::Pipe.

Linux box with a slightly modified version of your script, and the parent signalled from another shell:

#!/usr/bin/perl
use strict;
use warnings;

my $whoami;

sub handler {
   print {*STDERR} "$whoami: handler [@_]\n";
   exit 0;
}
$SIG{INT}  = \&handler;
$SIG{QUIT} = \&handler;
$SIG{TERM} = \&handler;
$SIG{PIPE} = \&handler;

END {
   print {*STDERR} "$whoami in END block\n";
}

print {*STDERR} qq{Parent PID $$\n};
pipe my $r, my $w;

my $pid;
if ($pid = fork) {
   $whoami = 'parent';
   close $w;
   print        {*STDERR} qq{Kid is PID $pid\n};
   while (<$r>) {
      print {*STDERR} "parent received: $_";
   }
   print {*STDERR} "parent exiting normally\n";
   exit 0;
} ## end if ($pid = fork)
elsif (defined($pid)) {
   select $w;
   $|++;
   $whoami = 'kid';
   close $r;
   print {$w} qq{Kid: Snoozing\n};
   for my $heartbeat (1 .. 30) {
      print {$w} qq{Kid: Heartbeat $heartbeat\n};
      sleep 1;
   }
   print {$w} qq{Kid: Waking\n};
   print {*STDERR} qq{Kid: Quitting\n};
   exit;
} ## end elsif (defined($pid))

__END__

poletti@PolettiX:~/sviluppo/perl$ perl johngg.pl
Parent PID 5336
Kid is PID 5337
parent received: Kid: Snoozing
parent received: Kid: Heartbeat 1
parent received: Kid: Heartbeat 2
parent received: Kid: Heartbeat 3
parent received: Kid: Heartbeat 4
parent received: Kid: Heartbeat 5
parent: handler [TERM]
parent in END block
poletti@PolettiX:~/sviluppo/perl$ kid: handler [PIPE]
kid in END block
[download]

Note that after the parent exits the shell regains control, hence the prompt. Within a second, the kid is trying to write to the pipe and gets signalled. Also note the following run (stopped with CTRL-C):

poletti@PolettiX:~/sviluppo/perl$ perl johngg.pl
Parent PID 5348
Kid is PID 5349
parent received: Kid: Snoozing
parent received: Kid: Heartbeat 1
parent received: Kid: Heartbeat 2
parent received: Kid: Heartbeat 3
parent: handler [INT]
parent in END block
kid: handler [INT]
kid in END block
[download]

Both processes get the INT signal: probably the shell sends the signal to the whole process group.