Beginning new section of the tutorial

src/2-2-conditionals-exceptions.md

@@ -520,3 +520,10 @@ Catala is able to express a wide range of legal text logic, and helps keeping
 the code alongside its specification.
 
 ## Checkpoint
+
+This concludes the second section of the tutorial. In Catala, variables can be
+defined piece-wise, each piece of definition being activate by a condition. When
+multiple conditions apply, one can prioritize the conditional definitions using
+the `exception` and `label` keywords to form exception trees able to capture the
+complex logic behind the legal texts while conserving the same structure as
+them.

src/2-3-list-modular.md

@@ -0,0 +1,6 @@
+# Going modular with lists
+
+In this section, the tutorial tackles a common pattern that significantly
+increases the complexity of a codebase: the need to deal with lists and rules
+applying to each element of the list. Here, Catala reuses all the common tricks
+from functional programming to ease

src/SUMMARY.md

@@ -10,7 +10,7 @@
 - [Tutorial : computing your taxes](./2-0-tutorial.md)
     - [Basic blocks of a Catala program](2-1-basic-blocks.md)
     - [Conditional definitions and exceptions](2-2-conditionals-exceptions.md)
-    - [Going modular](2-3-modular.md)
+    - [Going modular with lists](2-3-list-modular.md)
 - [Setting up a Catala project](./3-project.md)
 - [FAQ: How to code the law?](./4-0-howto.md)
     - [Usual design patterns](./4-1-design.md)