string uuid = "secondlife:///app/group/3fdf9db9-39c6-604f-3337-46caca3e4637/about"; //Put your group's UUID in here.
string groupName = "TFS"; //Put your group's name in here.

default
{
    touch_start(integer total_number)
    {
        llSay(0, "Open chat and click this link to join " + groupName + ": secondlife:///app/group/" + uuid + "/about");
    }
}