#!/usr/bin/perl## Turn name server debugging on or off.  ## To turn off debugging, use "binddebug 0"# To turn on debugging to level 3, use "binddebug 3"# Find the process ID in /etc/named.pid.open(PID, "/etc/named.pid") || die "Can\'t open /etc/named.pid\n";$pid = <PID>;chop($pid);$pid || die "No process ID in /etc/named.pid\n";# Get the debugging level from the command line.$savelevel = $level = $ARGV[0];$level =~ /^[0-9]+$/ || die "Integer argument required\n";# Turn off debugging if it is on.if(!kill 'USR2', $pid){ die "Kill of process ID $pid failed.\n"; }if($level == 0){  print "Debugging turned off.\n";} else {  while($level-- > 0) {     select(undef, undef, undef, 0.25);  # spread out signals    kill 'USR1', $pid;   }  printf "Name server now at debugging level $savelevel.\n";}