[d5ve]

Damian Conway's https://metacpan.org/pod/PPR module defines a regex (in the commonly used sense) that can match perl source code - including perl regexes!

Edit: "The PPR module provides a single regular expression that defines a set of independent subpatterns suitable for matching entire Perl documents, as well as a wide range of individual syntactic components of Perl (i.e. statements, expressions, control blocks, variables, etc.)"