subrule

Still being revised, but the current version is:

token term {
    [ <scoped_variables>
    | <variable>
    | <subroutine>
    | <block>
    | <regex_term>
    | <number>
    | <integer>
    | <string_literal>
    | <listop> [ <postop> | <listop_expression> ]?
    | <circumfix>
    ] <postop>*
}