my $i=0
my $blanked = 0;
open (IN, "xscreensaver-command -watch |");
while (<IN>) {
    if (m/^(BLANK|LOCK)/) {
        if (!$blanked) {
         system "cpufreq-set -f 700MHz";
         $blanked = 1;
        }
    } elsif (m/^UNBLANK/) {
        system "cpufreq-set -f 2.80GHz";
        $i=0;
        $blanked = 0;
    }
     elsif (m/^RUN/) {
        i++
       if ($i>4)
        system "xfce4-session-logout";
        $blanked = 0;
        }
    }
}