Blows the compiler heap, why?

heapboom.clj

(def pp                                                                                                                                                                                                                                                                         
  (λ [f xs]                                                                                                                                                                                                                                                                     
      (reduce ƒ(concat %1 (list (f %2))) '() xs))  )                                                                                                                                                                                                                            
                                                                                                                                                                                                                                                                                
(def pppp                                                                                                                                                                                                                                                                       
  (->> (pp inc (range))                                                                                                                                                                                                                                                         
       (drop (dec 1e6))                                                                                                                                                                                                                                                         
       (take 2)))