Here is 2 pcretest listings: 1. PCRE2 version 10.35 2020-05-09 /a\K.(?0)*/ abac 0: bac Expected result: c Perl's result: c 2. /a\Kb/replace=-$0- ab 1: a-b- PCRE doc's says about $<n> substitutions: "The number may be zero to include the entire matched string."But really we can see that entire matched string "ab" is not included in substitution.
So there is need to change either doc's or pcre2_substitute() behaviour --## List details at https://lists.exim.org/mailman/listinfo/pcre-dev
