Updated SC2002 (markdown)

SC2002.md

@@ -2,11 +2,16 @@
 
 ### Problematic code:
 
-    cat file | tr ' ' _
+```sh
+cat file | tr ' ' _ | grep a_
+```
 
 ### Correct code:
 
-    tr ' ' _ < file
+```sh
+tr ' ' _ < file | grep a_
+< file tr ' ' _ | grep a_ # notice: simple commands only -- won't work with componds
+```
 
 ### Rationale: