#!/usr/bin/perl -w 

use strict; 
use IO::Select; 
use IO::Pipe;

  my $fromchild = new IO::Pipe;
  my $tochild = new IO::Pipe;
  my $pid;
  my $parent_pid = $$;
  if($pid = fork()) { # Parent
   $fromchild->reader();
   $fromchild->autoflush(1);
   $fromchild->blocking(1);
   binmode $fromchild;
   $tochild->writer();
   $tochild->autoflush(1);
   $tochild->blocking(1);
   binmode $tochild;

   my $read_set = new IO::Select(); # create handle set for reading
   $read_set->add($fromchild);

   while(1) {
    print "before select\n";
    my ($rh_set, undef, $ex_set) = IO::Select->select($read_set, undef, $read_set, 30);
    print "after select\n";
    for my $rh (@$rh_set) {
	    my $s =  <$rh>;
	    print "command: $s";
    }
   }
  } elsif (defined ($pid)) { # Child
   $fromchild->writer();
   $fromchild->autoflush(1);
   $fromchild->blocking(1);
   binmode $fromchild;
   $tochild->reader();
   $tochild->autoflush(1);
   $tochild->blocking(1);
   binmode $tochild;
   print $fromchild "abc\n";
   #sleep(1);  ### IF you uncomment this line it will work
   print $fromchild "def\n";

   sleep(86400);
   die;
  }

__END__

=Output=:
$ ./poc1.pl
before select
after select
command: abc
before select

(process hangs here)