If you already know the process id(s), and own the processes, the kill builtin function might be of use.
in reply to Identifying whether a process is running
From the doco:
kill SIGNAL, LIST
$cnt = kill 1, $child1, $child2
kill 9, @goners;
If SIGNAL is zero, no signal is sent to the process, but the
kill(2) system call will check whether it's possible to send
a signal to it (that means, to be brief, that the process is
owned by the same user, or we are the super user). This is
a useful way to check that a child process is alive.