:l shell.hs
:def shell (\s -> do shell s; return "")
:l

:shell rm -f T6106.hs
:shell echo "{-# OPTIONS_GHC -F -pgmF ./T6106_preproc #-}" >T6106.hs
:shell echo "module T6106 where" >>T6106.hs
:load T6106.hs
-- second one should fail:
:reload