Restore example of conditional logic in expressions

Author: Scotchester

content/actions/reference/workflows-and-actions/expressions.md

@@ -83,6 +83,19 @@ env:
 
 {% data variables.product.prodname_dotcom %} provides a way to create conditional logic in expressions using binary logical operators (`&&` and `||`). This pattern can be used to achieve similar functionality to the ternary operator (`?:`) found in many programming languages, while actually using only binary operators.
 
+### Example
+
+{% raw %}
+
+```yaml
+env:
+  MY_ENV_VAR: ${{ github.ref == 'refs/heads/main' && 'value_for_main_branch' || 'value_for_other_branches' }}
+```
+
+{% endraw %}
+
+In this example, we're using a combination of `&&` and `||` operators to set the value of the `MY_ENV_VAR` environment variable based on whether the {% data variables.product.prodname_dotcom %} reference is set to `refs/heads/main` or not. If it is, the variable is set to `value_for_main_branch`. Otherwise, it is set to `value_for_other_branches`. It is important to note that the first value after the `&&` must be truthy. Otherwise, the value after the `||` will always be returned.
+
 ## Functions
 
 {% data variables.product.prodname_dotcom %} offers a set of built-in functions that you can use in expressions. Some functions cast values to a string to perform comparisons. {% data variables.product.prodname_dotcom %} casts data types to a string using these conversions: