Raku provides a superset of Perl 5 features with respect to regexes, folding them into a larger framework called "rules", which provide the capabilities of a parsing expression grammar, as well as acting as a closure with respect to their lexical scope. Rules are introduced with the codice_1 keyword, which has a usage quite similar to subroutine definitions. Anonymous rules can be introduced with the codice_2 (or codice_3) keyword, or simply be used inline as regexes were in Perl 5 via the codice_4 (matching) or codice_5 (substitution) operators.