- Tokens that use double quoted strings or regexes do interpolation.
- Hence, they can be make context sensitive, by referring to other
items in the production rule. For instance, by interpolating
- The <matchrule:...> is another way of building dynamic
rules. The part after the colon is evaluated as a double quoted
string each time the directive is encountered,
and the value it evaluates to is taken as the name of the subrule to