like this:

    //  split the message
    $word = explode(" ",$message);

    // the first word is the trigger, usually
    if($word[0] == "!trigger") {    
            send("PRIVMSG",$chan,"this is a test");
        }
    }

send($what,$to,$text) is to send usually PRIVMSGs, which are, in IRC Protocol the normal messages and formats it for IRC

sendsimple($what,$value) is to send messages like QUIT, where $value can be a quit message