send SIGSTOP to firefox when the workstation is locked, in order to save the CPU power

stop_firefox.pl

#!/usr/bin/perl

my $cmd = "dbus-monitor --session \"type='signal',interface='org.gnome.ScreenSaver',member='ActiveChanged'\"";

open (IN, "$cmd |");

while (<IN>) {
    if (m/^\s+boolean true/) {
        print "*** Screensaver is active ***\n";
        system("killall -s SIGSTOP firefox plugin-container");
    } elsif (m/^\s+boolean false/) {
        print "*** Screensaver is no longer active ***\n";
        system("killall -s SIGCONT firefox plugin-container");
    }
}