[Perl/perl5] d28cf2: Document and test command-line switch '-?'

[James E Keenan via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: d28cf2c2854ef1507811a5f4fb3d309c60987498
      
https://github.com/Perl/perl5/commit/d28cf2c2854ef1507811a5f4fb3d309c60987498
  Author: James E Keenan <jkee...@cpan.org>
  Date:   2021-12-24 (Fri, 24 Dec 2021)

  Changed paths:
    M pod/perlrun.pod
    M t/run/switches.t

  Log Message:
  -----------
  Document and test command-line switch '-?'