if($_ =~ /^:([^!]*)!(\S*) PRIVMSG (#\S+) :(.*)$/){
   my $user = $1;
   my $host = $2;
   my $chnl = $3;
   my $message = $4;
   if ($chnl eq $channel) {
      if ($message =~ /^!quit$/){
         die "Quiting!\n";
      }
      ...
   }
}