Updated var to work like jq #934

pkg/yqlib/doc/Style.md

@@ -18,7 +18,7 @@ a:
 ```
 
 ## Update and set style of a particular node using path variables
-You can use a variable to re-use a path
+You can use a variable reference to re-use a path
 
 Given a sample.yml file of:
 ```yaml
@@ -28,7 +28,7 @@ a:
 ```
 then
 ```bash
-yq eval '.a.b as $x | $x = "new" | $x style="double"' sample.yml
+yq eval '.a.b ref $x | $x = "new" | $x style="double"' sample.yml
 ```
 will output
 ```yaml

pkg/yqlib/doc/Variable Operators.md

@@ -1,4 +1,6 @@
-For more complex scenarios, variables can be used to hold values of expression to be used in other expressions.
+Like the `jq` equivalents, variables are sometimes required for the more complex expressions (or swapping values between fields).
+
+Note that there is also an additional `ref` operator that holds a reference (instead of a copy) of the path, allowing you to make multiple changes to the same path.
 
 ## Single value variable
 Given a sample.yml file of:
@@ -56,3 +58,37 @@ title: A well-written article
 author: Person McPherson
 ```
 
+## Using variables to swap values
+Given a sample.yml file of:
+```yaml
+a: a_value
+b: b_value
+```
+then
+```bash
+yq eval '.a as $x  | .b as $y | .b = $x | .a = $y' sample.yml
+```
+will output
+```yaml
+a: b_value
+b: a_value
+```
+
+## Use ref to reference a path repeatedly
+Given a sample.yml file of:
+```yaml
+a:
+  b: thing
+  c: something
+```
+then
+```bash
+yq eval '.a.b ref $x | $x = "new" | $x style="double"' sample.yml
+```
+will output
+```yaml
+a:
+  b: "new"
+  c: something
+```
+

pkg/yqlib/doc/headers/Variable Operators.md

@@ -1 +1,3 @@
-For more complex scenarios, variables can be used to hold values of expression to be used in other expressions.
+Like the `jq` equivalents, variables are sometimes required for the more complex expressions (or swapping values between fields).
+
+Note that there is also an additional `ref` operator that holds a reference (instead of a copy) of the path, allowing you to make multiple changes to the same path.