File :: RULES '%%' PERL

RULES :: RULE ATTRS

RULE :: lhs '--->' RHS
      | lhs '--->'

RHS :: RHS rhs
     | rhs

rhs :: word symbol

ATTRS :: ATTRS ATTR
       | ATTR

ATTR :: '::' word LIST '{' PERLCODE '}'

LIST ::
      | '[' LIST1 ']'

LIST1 :: word
       | word ',' LIST1