=over

=item kill SIGNAL, LIST

=item kill SIGNAL
X<kill> X<signal>

Sends a signal to a list of processes.  Returns the number of
processes successfully signaled (which is not necessarily the
same as the number actually killed).

    $cnt = kill 1, $child1, $child2;
    kill 9, @goners;

If SIGNAL is zero, no signal is sent to the process, but C<kill>
checks whether it's I<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 useful to check that a child process is still
alive (even if only as a zombie) and hasn't changed its UID.  See
L<perlport> for notes on the portability of this construct.

Unlike in the shell, if SIGNAL is negative, it kills process groups instead
of processes.  That means you usually
want to use positive not negative signals.
You may also use a signal name in quotes.

The behavior of kill when a I<PROCESS> number is zero or negative depends on
the operating system.  For example, on POSIX-conforming systems, zero will
signal the current process group and -1 will signal all processes.

See L<perlipc/"Signals"> for more details.

On some platforms such as Windows where the fork() system call is not available.
Perl can be built to emulate fork() at the interpreter level.
This emulation has limitations related to kill that have to be considered,
for code running on Windows and in code intended to be portable.

See L<perlfork> for more details.

If there is no I<LIST> of processes, no signal is sent, and the return
value is 0.  This form is sometimes used, however, because it causes
tainting checks to be run.  But see
L<perlsec/Laundering and Detecting Tainted Data>.

Portability issues: L<perlport/kill>.

=back