For one, @Pathmark would denote that Next Actions belong on the list for when you are in the 'pathmark context'. I'm assuming you're looking to make a shopping list, in which case, according to the way GTD is supposed to work, that would not make sense. Oranges, bananas, and soy milk, are not next actions that move an outcome to completion. They are items that belong on a list.
A @Pathmark list could certainly exist though. Let's say I find myself in pathmark frequently and there are things that I need to do there. My @Pathmark list might look like this:
-Dump change into the change machine
-Yell at customer service re my rotten tomatoes and sour grapes
-Look at pathmark shopping list for items to buy (if you want to get into the nitty gritty)
And so on...
However, I am rather new at this, and I have my own newbie questions. But for me at least, the function of context lists seems straightfoward.