The keyword sequence 'X' is deprecated; use 'Y' instead.
where X is the form supported in older versions of the language, Y
the recommended form.
Obsolete forms of the language include the verbose comparison
operators (such as using 'IS EQUAL' instead of '='), '=' for
pattern-assignment instead of '=>', and the names SGML and OUTPUT
instead of #MARKUP-PARSER and #CURRENT-OUTPUT. Such forms are subject
to eventual removal from the language.