I build & use the latest Postfix release from source instead of depending on distro packages.
I use regex alot, including in Postfix. I try to keep up to date with upstream PCRE too.
PCRE has released a v2, where all new features appear, and maintains (bug-fixes only) v1.
There are two major versions of the PCRE library. The newest version, PCRE2, was released in 2015 and is at version 10.21. The original, very widely deployed PCRE library, originally released in 1997, is at version 8.38, and the API and feature set are stable—future releases will be for bugfixes only. All new future features will be to PCRE2, not the original PCRE 8.x series.
Currently my Postfix build links to latest PCRE v1