Terminology of Parse::RecDescent

• Grammar consists of a set of rules.
• Each rule starts with an identifier (which corresponds to a non-terminal), followed by a colon, followed by zero or more productions, separated by vertical bars.
• If there is more than one production for a rule, they are alternatives, and a similar effect can be reached by having several rules starting with the same identifier.
• Each production consists of zero or more items.
• Items are:
  • Subrule: another rule to be matched.
  • Token: a literal or a regex to be matched. This has to match at the beginning of the unparsed part of the to be parsed string - skipping over any leading whitespace. This corresponds to the so-called terminals.
  • Action: a piece of Perl code to be executed.
  • Directive: a special instruction to the parser.
  • Comment: a standard Perl comment.