<copy>

>--- COPY --- <id> ----+--- REName --- name --- name ---.
                       |                                |
                       ‘--------------------------------+---><uval>

>---+--- value ----------.
    |                    |
    ‘--- <expression> ---+--- EXponential --- value ---.
                         |                             |
                         ‘-----------------------------+--- MM -------.
                                                       |              |
                                                       |--- Metres ---|
                                                       |              |
                                                       |--- INches ---|
                                                       |              |
                                                       |--- FT -------|
                                                       |              |
                                                       |--- FEet -----|
                                                       |              |
                                                       |--- text -----|
                                                       |              |
                                                       ‘--------------+--->