Each command is described by a string specifying what is expected.
This can be displayed by ending the input line with a '?', when the program will
give the string as a prompt. All previous input is retained.  To investigate a
command, type '<command> ?' and then give an invalid response once the string
has been displayed. The single character '=' is always invalid.

The string represents a set of attributed items, separated by commas, with
possible aliases indicated by '='.  Items may be matched by position, or by
quoting the keyword, then an optional '=', and then the value.

To insert an item value that is the same as one of the keywords, or contains
spaces, then it should be enclosed in double quotes, e.g. "The subject matter".

The attributes are:
        /A      This item must be supplied
        /K      This item must be keyed if it occurs
        /S      This item is a switch, that is there is no associated value

Thus item/a,to,subject=about/K will match any of
        1 fred subject wombats
        1 to fred about wombats
        about wombats to=fred item = 1

When a mail item is to be selected, the number of the item concerned may be
types, or one of F, L, N or '.', meaning the First, Last, Next or current item
(the current item is marked with a '=>' in the item field).

If a group of items may be selected, then '*' may be given to mean the previous
group, or a set of item selectors may be given.  An item selecetor may be an
item, or a pair of items seperated by a '-', to indicate all those bewteen the
first item given and the second.  Thus 'f-l' is the same as matching the switch
ALL.


