diff --git a/src/test/rustdoc-json/nested.rs b/src/test/rustdoc-json/nested.rs
index f32692b70cd..2e0179113ac 100644
--- a/src/test/rustdoc-json/nested.rs
+++ b/src/test/rustdoc-json/nested.rs
@@ -7,15 +7,18 @@
 // @is nested.json "$.index[*][?(@.name=='l1')].kind" \"module\"
 // @is - "$.index[*][?(@.name=='l1')].inner.is_crate" false
 // @count - "$.index[*][?(@.name=='l1')].inner.items[*]" 2
+// @set l1_id = - "$.index[*][?(@.name=='l1')].id"
 pub mod l1 {
 
     // @is nested.json "$.index[*][?(@.name=='l3')].kind" \"module\"
     // @is - "$.index[*][?(@.name=='l3')].inner.is_crate" false
     // @count - "$.index[*][?(@.name=='l3')].inner.items[*]" 1
+    // @set l3_id = - "$.index[*][?(@.name=='l3')].id"
     pub mod l3 {
 
         // @is nested.json "$.index[*][?(@.name=='L4')].kind" \"struct\"
         // @is - "$.index[*][?(@.name=='L4')].inner.struct_type" \"unit\"
+        // @set l4_id = - "$.index[*][?(@.name=='L4')].id"
         pub struct L4;
     }
     // @is nested.json "$.index[*][?(@.inner.span=='l3::L4')].kind" \"import\"
diff --git a/src/tools/jsondocck/src/cache.rs b/src/tools/jsondocck/src/cache.rs
index b742f0eb3ee..8a6a911321c 100644
--- a/src/tools/jsondocck/src/cache.rs
+++ b/src/tools/jsondocck/src/cache.rs
@@ -9,6 +9,7 @@ pub struct Cache {
     root: PathBuf,
     files: HashMap<PathBuf, String>,
     values: HashMap<PathBuf, Value>,
+    pub variables: HashMap<String, Value>,
     last_path: Option<PathBuf>,
 }
 
@@ -19,6 +20,7 @@ impl Cache {
             root: Path::new(doc_dir).to_owned(),
             files: HashMap::new(),
             values: HashMap::new(),
+            variables: HashMap::new(),
             last_path: None,
         }
     }
diff --git a/src/tools/jsondocck/src/main.rs b/src/tools/jsondocck/src/main.rs
index 2afb66b9696..9f231842c60 100644
--- a/src/tools/jsondocck/src/main.rs
+++ b/src/tools/jsondocck/src/main.rs
@@ -49,6 +49,7 @@ pub enum CommandKind {
     Has,
     Count,
     Is,
+    Set,
 }
 
 impl CommandKind {
@@ -56,6 +57,7 @@ impl CommandKind {
         let count = match self {
             CommandKind::Has => (1..=3).contains(&args.len()),
             CommandKind::Count | CommandKind::Is => 3 == args.len(),
+            CommandKind::Set => 4 == args.len(),
         };
 
         if !count {
@@ -85,6 +87,7 @@ impl fmt::Display for CommandKind {
             CommandKind::Has => "has",
             CommandKind::Count => "count",
             CommandKind::Is => "is",
+            CommandKind::Set => "set",
         };
         write!(f, "{}", text)
     }
@@ -130,6 +133,7 @@ fn get_commands(template: &str) -> Result<Vec<Command>, ()> {
             "has" => CommandKind::Has,
             "count" => CommandKind::Count,
             "is" => CommandKind::Is,
+            "set" => CommandKind::Set,
             _ => {
                 print_err(&format!("Unrecognized command name `@{}`", cmd), lineno);
                 errors = true;
@@ -236,6 +240,23 @@ fn check_command(command: Command, cache: &mut Cache) -> Result<(), CkError> {
                 Err(_) => false,
             }
         }
+        // FIXME, Figure out semantics for @!set
+        CommandKind::Set => {
+            // @set <name> = <path> <jsonpath>
+            assert_eq!(command.args.len(), 4);
+            assert_eq!(command.args[1], "=", "Expected an `=`");
+            let val = cache.get_value(&command.args[2])?;
+
+            match select(&val, &command.args[3]) {
+                Ok(results) => {
+                    assert_eq!(results.len(), 1);
+                    let r = cache.variables.insert(command.args[0].clone(), results[0].clone());
+                    assert!(r.is_none(), "Name collision");
+                    true
+                }
+                Err(_) => false,
+            }
+        }
     };
 
     if result == command.negated {