Clicker = function(prefix, callback) {
    this.prefix = prefix + '__';
    this.callback = callback;
    $$('[id^="' + this.prefix + '"]').invoke('observe', 'click', this.onClick.bind(this));
}

Clicker.prototype.onClick = function(e) {
    this.callback(e.element().id.substr(this.prefix.length));
}