Fix typo

Author: naskya

markdown/source_md/modules.md

@@ -277,7 +277,7 @@ The first list contains everything the resulting list from `takeWhile` would con
 The second list contains the part of the list that would have been dropped.
 
 ```{.haskell:ghci}
-ghci> let (fw, rest) = span (/=' ') "This is a sentence" in "First word:" ++ fw ++ ", the rest:" ++ rest
+ghci> let (fw, rest) = span (/=' ') "This is a sentence" in "First word: " ++ fw ++ ", the rest:" ++ rest
 "First word: This, the rest: is a sentence"
 ```