Tweak regex pattern

src/Util/YamlSourceManipulator.php

@@ -684,7 +684,7 @@ private function getEndOfPreviousKeyPosition($key): int
 
     private function getKeyRegex($key)
     {
-        return sprintf('#\b%s\'?( )*:#', preg_quote($key));
+        return sprintf('#(?<!\w)\$?%s\'?( )*:#', preg_quote($key));
     }
 
     private function updateContents(string $newContents, array $newData, int $newPosition)

tests/Util/yaml_fixtures/add_item_on_config_with_bind.test

@@ -0,0 +1,28 @@
+services:
+  _defaults:
+    autowire: true
+    autoconfigure: true
+    bind:
+      $httpClient: '@http.client'
+
+  app.service:
+    class: App\Services\Service
+    arguments:
+      - argument_1: something
+        argument_2: something
+===
+$data['services']['app.service']['arguments']['argument_3'] = 'something_new';
+===
+services:
+  _defaults:
+    autowire: true
+    autoconfigure: true
+    bind:
+      $httpClient: '@http.client'
+
+  app.service:
+    class: App\Services\Service
+    arguments:
+      - argument_1: something
+        argument_2: something
+        argument_3: something_new