diff --git a/how-it-works.md b/how-it-works.md
index 9f36a2b5..51a41fcd 100644
--- a/how-it-works.md
+++ b/how-it-works.md
@@ -37,7 +37,7 @@ The `=` operator then pipes the 'root' context through the `rhs` expression of `
 dog
 ```
 
-Both sides have now been evaluated, so now the operator copies across the value from the RHS (`.b`) to the the LHS (`.a`), and it returns the now updated context:
+Both sides have now been evaluated, so now the operator copies across the value from the RHS (`.b`) to the LHS (`.a`), and it returns the now updated context:
 
 ```yaml
 a: dog
diff --git a/operators/alternative-default-value.md b/operators/alternative-default-value.md
index a1a3208a..1c70d0cb 100644
--- a/operators/alternative-default-value.md
+++ b/operators/alternative-default-value.md
@@ -79,3 +79,36 @@ will output
 cat
 ```
 
+## Update or create - entity exists
+This initialises `a` if it's not present
+
+Given a sample.yml file of:
+```yaml
+a: 1
+```
+then
+```bash
+yq '(.a // (.a = 0)) += 1' sample.yml
+```
+will output
+```yaml
+a: 2
+```
+
+## Update or create - entity does not exist
+This initialises `a` if it's not present
+
+Given a sample.yml file of:
+```yaml
+b: camel
+```
+then
+```bash
+yq '(.a // (.a = 0)) += 1' sample.yml
+```
+will output
+```yaml
+b: camel
+a: 1
+```
+