This DrRacket plugin adds a Script menu to the main window.
This menu has several items, followed by the (initially empty) list of active 
scripts.

The New Script item asks for a script name and creates 2 files:
    - a .rkt file, the script itself (with a sample program)
    - a .rktd file, the metadata of the script with the default values
These two files are automatically opened.

The .rkt file:
    This is the script file.
    It must provide the 'transform-input-string' (that's not a very good name) 
    function, as in the sample code.
    It is meant to be executable by itself, to ease the testing process.

The .rktd file:
    - most options are the same as for the menu-item% constructor
    - sub-menu: string?
        A string for the label of the sub-menu in which the script will appear.
    - output-to: (one-of 'selection 'new-tab 'message-box)
        If 'selection, the output of the transform function replaces the 
        selection in the current tab (or insert at the cursor if there is no 
        selection).
        If 'new-tab, a new tab is created and 
     if #t the result of the script is output in a new tab and not 
    in the current window

The script menu is rebuild each time the user activates it, so that changes
are taken into account as soon as possible.

The default location of the scripts is in a subfolder of 
(find-system-path 'home-path).
The directory of the user scripts can be change through DrRacket's preferences
(in Edit/Preferences/Scripts).