diff --git a/makefile.md b/makefile.md
index 1c457d461..4632c8d6c 100644
--- a/makefile.md
+++ b/makefile.md
@@ -11,6 +11,7 @@ category: CLI
 uglify = $(uglify)        # lazy assignment
 compressor := $(uglify)   # immediate assignment
 prefix ?= /usr/local      # safe assignment
+hello += world                # append
 ```
 
 `=` expressions are only evaluated when they're being used.