integer root = 0 ; // change to the number of a prim that you want to flash
float timeval = 0.1; //the interval between events, smaller = faster
integer counter = 0;

On() {
    llSetLinkPrimitiveParamsFast(root,[PRIM_POINT_LIGHT, TRUE, <1,1,1>, 1.0, 10, .1, PRIM_FULLBRIGHT, ALL_SIDES,TRUE, PRIM_GLOW, ALL_SIDES, 1.0]);
}
Off() {
    llSetLinkPrimitiveParamsFast(root,[PRIM_POINT_LIGHT, FALSE, <1,1,1>, 1.0, 10, .1, PRIM_FULLBRIGHT, ALL_SIDES,FALSE, PRIM_GLOW, ALL_SIDES, 0.0]);
}
default
{
    state_entry()
    {
        Off();
    }
    touch_start(integer total_number)
    {
        llSetTimerEvent(timeval); // between events
    }
    timer()
    {
        if (counter == 0)
            On();
        else if (counter == 1)
            Off();
        else if (counter == 2)
            On();
        else if (counter >= 3) {
            Off();
            counter = -1;
            llSetTimerEvent(0);
        }
        counter++;
    }   
}