Haskell's tools for modularity cut in a dimension you're not used to, and if you're not experienced with it, won't see. Percentage-wise in the last 15 years I haven't spent that much time in Haskell, but it's Haskell's tools I'm missing more often in imperative languages than the other way around. (And note the "more often"; it's not that I never miss more conventional tools in Haskell, it's just that I spend more time missing Haskell tools in other languages.)