Having done plenty of interviews, it's surprising how many candidates list every technology they may have touched for the briefest of moments. For me, "grilling" someone on something like a programming language is about determining if they've _really_ used it or not.
If a candidate lists multiple languages on their resume, I'll often ask them to do a compare and contrast -- what do they think are the strengths and weaknesses of the languages? What did you use language X for? Do you think language Y would have been better/worse/same to attack the same problem?
I'm not looking to trip them up, just find out if their resume is an accurate reflection of their experience.
"I used it so I wouldn't need to rewrite the 300 proprietary internal libraries and dependencies our company also paid to write and maintain in that language" is probably a valid answer for many BigCo employees.
If a candidate lists multiple languages on their resume, I'll often ask them to do a compare and contrast -- what do they think are the strengths and weaknesses of the languages? What did you use language X for? Do you think language Y would have been better/worse/same to attack the same problem?
I'm not looking to trip them up, just find out if their resume is an accurate reflection of their experience.