mod131.hs:2:27:
    Conflicting exports for `f':
      `module Mod131_B' exports `f' imported from Mod131_B at mod131.hs:3:17
                                      (defined at Mod131_B.hs:3:1)
      `Mod131_A.f' exports `Mod131_A.f' imported from Mod131_A at mod131.hs:4:27
                                          (defined at Mod131_A.hs:3:1)