the result is `yes`. Things to watch out for: the expression after the equal sign must have balanced parentheses,
and the "in" is obligatory. If you violate these rules, the system will still produce a result, but it won't make much sense.
-*Abbreviations*: No abbreviations work. So `\xy.yxx` must be written `(\x (\y ((y x) x)))`. (As in Scheme or Racket.)
+*Abbreviations*: No abbreviations work. So `\xy.yxx` must be written `(\x (\y ((y x) x)))`.
*Comments*: anything following a semicolon to the end of the line is ignored.
Blank lines are fine.