if ($pid = fork) { # parent
   ...
}
elsif ($pid == 0) { child
   ...
   exit;
}

##</code><code>##

pipe(PIPE_READ,PIPE_WRITE);
autoflush PIPE_WRITE 1;
#my $pid = fork();
if ($pid = fork) { # parent
  $SIG{CHLD} = \&chld_handler;
  &read_pipe;         
} 
elsif (defined $pid) { # child
  &write_pipe ($pid); 
  exit;
}
else {
  die "cannot fork: $!";
}

sub chld_handler {
    warn "parent got signal @_\n";
    waitpid($pid,0);
    exit;
}

sub write_pipe {
    print "child pid $$ \n";
    while(1) {
        sleep 1;
        print "Enter message: ";
        my $usr_msg = <STDIN>;
        chomp $usr_msg;
        last unless $usr_msg;
        print "child pid = $$  message = $usr_msg\n";
        print PIPE_WRITE "$usr_msg\n";
    }
}

sub read_pipe {
    print "parent here. child pid = $pid\n";
    while ( my $msg_read = <PIPE_READ>) {
        print "received from pipe $msg_read";
    }
}