while(y.t<ys) y.(y.t++, 0);

// decompiles into

for(; y.t < ys; )
{
    var _loc21_:* = y;
    var _loc22_:* = 0;
    var _loc23_:* = new XMLList("");
    while(§§hasnext(y,_loc22_))
    {
        _loc20_ = §§nextvalue(_loc22_,_loc21_);
        with(_loc20_)
        {
            y.t = Number(y.t) + 1;
        }
    }
}