my $pid;
if (($pid = fork()) == 0) {
    # child process
    exec 'some/program','and', 'args';
} else {
    # parent process
    $SIG{'CHLD'} = \&sub_that_handles_child_exit_notify;
}
# dosomething with $pid...
my $is_alive = kill 0, $pid;  # see if still alive
kill 15, $pid;                # send a SIGTERM