diff --git a/snippets/grep.fish b/snippets/grep.fish
new file mode 100644
index 0000000..d229829
--- /dev/null
+++ b/snippets/grep.fish
@@ -0,0 +1,5 @@
+#!/usr/bin/env fish
+
+# Check unwanted data
+# Show file name and line number
+! grep -EHinr -e 'some' -e 'regexp' * || ( echo 'unwanted data found' >&2 && false )
diff --git a/snippets/lefthook.yml b/snippets/lefthook.yml
new file mode 100644
index 0000000..5a43957
--- /dev/null
+++ b/snippets/lefthook.yml
@@ -0,0 +1,7 @@
+---
+pre-commit:
+  commands:
+    check-unwanted-data:
+      run: >-
+        ! ( grep -Hin -e 'example.org' -e '012345678901' {staged_files} )
+        || ( printf %b '\n' 'found possibly unwanted data' >&2 && false )