Matheus Tavares Bernardino [off-list ref] writes:
I noticed we also have some uses of + and ? in tests, with `grep -E`
(or egrep). Are we OK with ERE or did these maybe just slip in by
accident?
We are OK with 'grep -E' and 'egrep' and write '+' and '?' as valid
ERE elements. What we are not OK with is to invoke ERE elements in
an expression that is supposed to be a BRE by prefixing a backslash,
e.g. '\+'. Perhaps it is a GNU extension?
We need to remove '\+' in t/perf/bisect_regression used with sed.
What is sad is that this trick and "sed -E" are both GNUisms, and
there is no portable way to use ERE with sed X-<.
But we could resort to Perl in truly tricky cases ;-).