How to combine multiple field values to create single field name in eval statement.

Hi, I'm trying to combine the values of multiple fields to together form a single field name in an eval if statement. Something like the example below. Is that in any way possible? Thanks for your help! | eval {operation}_{merchant}_{country}=if((operation=operation AND country=country AND merchant=merchant), {operation}_{merchant}_{country}+1, 0)