Drilling holes does not solve the problem and that allows outside elements to enter into the headlamp which could cause faster corrosion, rust, burnt bulb, etc... Your basically allowing O2 to enter into a sealed headlamp to evaporate the moisture...
Unfortunately, the only way to truely correct the problem is to remove the headlamp from the car... Then place the headlamp in the oven at 350 degrees for about 15 minutes or so to loosen the glue...What that does is loosen and make the lense glue soft so you can effectively remove the clear lense from the headlamp casing... You then can clean the lense with plexy glass cleaner and make it shine on both sides... This will make the head lamp look like new... Lastly go to the auto parts store near you and ask for the best adhesive gasket sealer they have (I used high temp silicon gasket sealer on my SC400 and ES300)...Both times the lamps came out as good as new and had no leaks.. I then of course had to do the other headlamps to match the newer looking ones... T
What you can also do if you don't want down time is to log onto Ebay and buy a like new head lamp for a couple of hundred and replace it with your fogged lamp... Then on your own free time you can do as I stated above and restore your fogged headlamp and then reseal it on Ebay and reclaim your money...
Hope that helps....