12.12  Except statements

“Easy writing makes damned hard reading.”
                                        —Richard Brinsley Sheridan

Multi-key except statements are implicit case statements. Lay them out accordingly.

The canonical layouts are

    expression
    except
        key = expression;

    expression
    except
        long_key
            =
            {   statement;
                statement;
                statement;
                ...
            };

    expression
    except
        key => expression;
        key => expression;
        key => expression;
        ...
    end;


    expression
    except
        long_key
            =>
            {   statement;
                statement;
                statement;
                ...
            };

        long_key
            =>
            {   statement;
                statement;
                statement;
                ...
            };

        long_key
            =>
            {   statement;
                statement;
                statement;
                ...
            };
    end;