gistfile1.txt

clunky env var1 var2 | ok1 && ok2 = val1 + val2
                     | otherwise  = var1 + var2
                          where
                            m1 = lookup env var1
                            m2 = lookup env var2
                            ok1 = maybeToBool m1
                            ok2 = maybeToBool m2
                            val1 = expectJust m1
                            val2 = expectJust m2
                            
clunky env var1 var2
 | Just val1 <- lookup env var1
 , Just val2 <- lookup env var2
 = val1 + val2
 | otherwise = var1 + var2