diff --git a/README.md b/README.md
index a28671e..ad60936 100644
--- a/README.md
+++ b/README.md
@@ -450,6 +450,10 @@ Usage: symbex [OPTIONS] [SYMBOLS]...
           return a + b + 3
       " | symbex my_function --replace
 
+      # Replace my_function with the output of a command:
+      symbex first_function --rexec "sed 's/^/# /'"
+      # This uses sed to comment out the function body
+
 Options:
   --version                  Show the version and exit.
   -f, --file FILE            Files to search
diff --git a/symbex/cli.py b/symbex/cli.py
index 215e647..4e47cdb 100644
--- a/symbex/cli.py
+++ b/symbex/cli.py
@@ -234,6 +234,11 @@ def cli(
             # This is a replacement implementation
             return a + b + 3
         " | symbex my_function --replace
+
+    \b
+        # Replace my_function with the output of a command:
+        symbex first_function --rexec "sed 's/^/# /'"
+        # This uses sed to comment out the function body
     """
     if modules:
         module_dirs = []