Hi, I have a program, structured approximately like so main = do let stage1 = e1... let stage2 = e2...stage1... stage3 <- e3...stage2 case something of foo -> output stage1 bar -> output stage2 baz -> output stage3 I think this is an improvement from using multiple main functions, since it reveals the pipeline structure of the program and the modularity of the stages. It appears¹, however, that naming the result of stage1 prevents it from being garbage collected when subsequent stages are produced. Since stage1 is a huge list, this leads to a space leak. So, is there any way to avoid this? Do I need to restructure my program? I could conceivably do main = do let stage1 = e1... let stage2 = e2...(e1...)... : and so on, but an aggressive (but slightly dumb) compiler might rediscover the similarity and CSE it. Suggestions more than welcome. -kzm ¹ Memory retainer profiling shows the product being retained by SYSTEM, so I *think* this is the right interpretation. -- If I haven't seen further, it is by standing in the footprints of giants