Reading Simple Haskell
I once downloaded a python script, ran it with some input, and got a result. Curious, I opened the script in Emacs, which then opened it into python mode. As is my habit, I indented the whole file, which did basic white space changes to it according to python mode. I didn't realize I did this at first, and I saved and exited the script,  then played around with it some more. Still got results, everything seemed the same. But when I tried it with the same input as originally, it was a different return result. This took a while to figure out, until I realized that emacs changed the indentation of just one line, because the author had apparently not followed the typical idioms or conventions of indenting python in some way. That merely opening, beautifying, and saving a file could change program output with no errors has turned me off of white space sensitive syntax ever since.Which is partly why OCaml gets some bias from me over Haskell.