When I started working in Westborough, my fellow employee and Westborough native, Brendan showed me all the good placed to eat.  Regatta Deli was one of our first lunchtime fieldtrips.
Inside is a small but not cramped space that you can sit in but it seemed most people (including us) got sandwiches to go.
They have a dry erase board behind the counter with their hand-written menu.
Since this was my first time here, I felt compelled to get their famous regatta club which has various cold cuts, cheeses, lettuce, tomato, pickles and I think I got oil and vinegar on it.

This was excellent.  The bread was fresh and the combination of all the ingredients was delicious.
It was a tough call for Brendan but he went with some sort of turkey and bacon sub and had an equally satisfying experience.

He insisted on having me take a picture of it open to show all the goodness:

I actually ended up bringing almost half of my sub home to Ethan and he enjoyed it as well.  This is well worth the $4.  In fact the whole menu is a bargain.  This is a great place, you can check out their menu on their site.  Don’t mind the lady in the upper left-hand corner taking a passionate bite out of her sandwich, maybe she just got off the juice-fasting diet.