frisby is a parser library that can parse arbitrary PEG grammars in linear time. Unlike other parsers of PEG grammars, frisby need not be supplied with all possible rules up front, allowing composition of smaller parsers. . PEG parsers are never ambiguous and allow infinite lookahead with no backtracking penalty. Since PEG parsers can look ahead arbitrarily, they can easily express rules such as the maximal munch rule used in lexers, meaning no separate lexer is needed. . In addition to many standard combinators, frisby provides routines to translate standard regex syntax into frisby parsers.