[Perl/perl5] 0cca55: gh18770: stop scanning for substrs after *COMMIT

[Hugo van der Sanden via perl5-changes]

  Branch: refs/heads/gh18770
  Home:   https://github.com/Perl/perl5
  Commit: 0cca55291a50cbe3c42098930c8ad09dd021cdf8
      
https://github.com/Perl/perl5/commit/0cca55291a50cbe3c42098930c8ad09dd021cdf8
  Author: Hugo van der Sanden <h...@crypt.org>
  Date:   2021-05-07 (Fri, 07 May 2021)

  Changed paths:
    M regcomp.c

  Log Message:
  -----------
  gh18770: stop scanning for substrs after *COMMIT