#!/usr/bin/perl

my $pid = fork;
die "fork: $!\n" unless defined $pid;

if( $pid ) {
  ## Parent
  print "Parent $$, child is $pid\n";

  for( 1..5 ) {
    check_alive( $pid );
    sleep 2;
  }
} else {
  ## Child
  print "Child here, pid $$; sleeping 7 secs\n";
  sleep 5;
  print "Child exiting\n";
  exit 0;
}

print STDERR "Parent, waiting on child\n";

waitpid( $pid, 0 )
  or warn "waitpid: $!\n";

check_alive( $pid );

exit 0;

sub check_alive {
  my $pid = shift;
  my $kill = kill 0 => $pid or warn "kill: $!\n";

  $kill = $kill == 1 ? "alive" : "$!";

  print STDERR scalar localtime, ": kill sez $kill\n";
}

__END__