bug#66753: grep 3.8 now needs pcre2 as input, not pcre

[Matt Beshara <m@mfa.pw>]

Hi Guix people,
I have been working on creating a package definition for 
pulseaudio-equalizer¹ and when built with the current definition 
of the grep package, it prints this error message when running:

grep: Perl matching not supported in a --disable-perl-regexp build
grep: write error: Broken pipe

Searching for that error message, I came across this:
https://trac.macports.org/ticket/65800

So it seems that, for version 3.8, the pcre input package for grep 
should be changed to pcre2.  I have made this change in a new 
definition which inherits grep and told my pulseaudio-equalizer 
package to use that as a propagated input, and that causes the 
error to go away.  For the sake of completeness, here’s the 
definition I used:

(define grep-fixed
  (package
    (inherit grep)
    (inputs (list pcre2))))

Best wishes,
Matt

1. https://github.com/pulseaudio-equalizer-ladspa/equalizer