Learn how to pronounce Worcestershire (it's worst-a-sure, not war-chester-shire). You're welcome...
Mix the beer, Worcestershire, the juice from one lime and cumin in a large bowl and combine thoroughly.
Place the steak in a large Ziplock bag, pour in the marinade and place in the refrigerator. Marinate the steak for 4 hours (at least 2), turning the bag occasionally.
Light the grill to high heat for direct grilling.
Remove the steak from the marinade and sprinkle with a generous amount of Kosher salt and fresh ground black pepper.
Flank steak cooks pretty quick, so don't overcook it. Remember, you can always throw it back on the grill for a few minutes if it needs more time. As always, these times are approximate and it always depends on the thickness of the meat and the temperature of your grill.
Place the flank steak over the hottest part of the grill and grill for about 4 - 6 minutes on each side for medium rare.
Let the flank steak rest for about 5 minutes on the cutting board to let the juices settle in the meat.
Slice thin, against the grain and serve with the left over beer!