2.3 Allow and Deny statements
These access control statements start allow or deny, followed by a single
token reason to be returned to the caller (thus the reason should be quoted if
it contains spaces), followed by zero or more definition names, all of which
must pass for the statement to execute.
For example:
allow "Administrators can do anything" is-admin deny "Plebs may do nothing" is-pleb allow ''
As with definitions, includes, etc, if rule names are prefixed with an exclamation point then their sense is inverted, e.g.
deny "Only admins may alter hooks" altering-hooks !is-admin