...................................................................
my $process = "ntop";

my $return = 'ps -eaf |grep $process |grep -v grep';

my $stop = '/usr/local/bin/sudo sh /usr/local/www/cgi-bin/ntop/ntop.sh stop &';

if ($return ne "" ) {
    system ($stop) and die "...";
}

sleep(8);

my $start = system('/usr/local/bin/sudo /usr/local/www/cgi-bin/ntop/ntop.sh start') and die "...";
...................................................................