Updated SC2152 (markdown)

SC2152.md

@@ -21,7 +21,7 @@ myfunc() {
 
 In many languages, `return` is used to return from the function with a final result.
 
-In bash, `return` can only be used to signal success or failure (0 = success, 1-255 = failure), more akin to `throw/raise` in other languages.
+In sh/bash, `return` can only be used to signal success or failure (0 = success, 1-255 = failure), more akin to `throw/raise` in other languages.
 
 Results should instead be written to stdout and captured:
 
@@ -30,7 +30,9 @@ message=$(myfunc)
 echo "The function wrote: $message"
 ```
 
-In functions that return small integers, such as getting the cpu temperature, the value should still be written to stdout. `return` should be reserved for error conditions, such as "can't determine CPU temperature".
+In functions that return small integers, such as getting the cpu temperature, the value should still be written to stdout. `return` should be reserved for error conditions, such as "can't determine CPU temperature". Error or failure messages should be written to stderr.
+
+Note in particular that `return -1` is equivalent to `return 255`, but that `return 1` is the more canonical way of expressing the first possible error code.
 
 ### Exceptions: