prepre in readme

README.md

@@ -11,9 +11,9 @@ file
 
 The package provides
 
- - `\grabbox<*>{<register>}[<pre>]{<mode>}[<post>]{<next>}`: grab the
+ - `\grabbox<*>[<prepre>]{<register>}[<pre>]{<mode>}[<post>]{<next>}`: grab the
    next argument as a box in `<mode>` (`\hbox`, `\vbox` or `\vtop`) and save it
    in box `<register>`. After the box is saved execute `<next>`. Inside of the
-   box one can inject `<pre>` before the contents and `<post>` after them. If
-   the star is not given spaces are stripped from the start and the end of the
-   box.
+   box one can inject `<prepre>` and `<pre>` before the contents and `<post>`
+   after them. If the star is not given spaces are stripped from the start and
+   the end of the box.