123.8 has the airspace from the Runway to Porpa and TD and beyond..
119.1 has the Airspace south of that line controlling the arrival flow to 07L/R
After T/O you need to call 123.8 first then switch to 119.1 if you turn south. If you keep going to TD you stay on 123.8
I'm sure smarter heads than ours have worked out this is the best way.
But it's still annoying.