install perl

.drone.yml

@@ -10,7 +10,7 @@ steps:
   - name: step1
     image: alpine
     commands:
-      - apk add git
+      - apk add perl git
       - changed_charts=$(git show --name-only --pretty="format:" | grep '^charts' | perl -pe 's/^([^\/]*?\/[^\/]*?)\/.*/$1/' | sort | uniq)
       - echo $changed_charts