[Perl/perl5] 1da21e: Update index() documentation with some code examples

[Scott Baker]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: 1da21e25b97e2ce86e1f2189ed99a79c3aebdeac
      
https://github.com/Perl/perl5/commit/1da21e25b97e2ce86e1f2189ed99a79c3aebdeac
  Author: Scott Baker <sc...@perturb.org>
  Date:   2020-07-17 (Fri, 17 Jul 2020)

  Changed paths:
    M pod/perlfunc.pod

  Log Message:
  -----------
  Update index() documentation with some code examples