...
my $pid = fork;
$pid == 0 and exec 'ping', '-c', '3', $site;
# child ($pid 0) never reaches code below.
# exec doesn't return, it can only exit
# or it can fail to find ping, but I use autodie
# (for this kind of program that's probably
# not a great idea in something
# that can be called 'production'... but w/e)

$kids{$pid} = $site; # only parent gets here
...