bug#53297: Provide option to use perl with grep

[Sébastien Lerique]

This seems to happen with any "grep -D" on my side, similar to
https://issues.guix.gnu.org/66753 .

  $ echo AAA | grep -P AA
  grep: Perl matching not supported in a --disable-perl-regexp build
  $ echo AAA | grep AA
  AAA

(in my case, trying out fasd in fish
<https://github.com/fishgretel/fasd/blob/9a16eddffbec405f06ac206256b0f7e3112b0e2c/conf.d/__fasd_run.fish#L2>)

Any hint for what's going on?