Re: PL_stashcache, or, what's our minimum Perl version?

I wrote:
> Done. I have also reconfigured buildfarm member prairiedog to use
> a non-MULTIPLICITY build of Perl 5.8.3, with the oldest Test::More
> and IPC::Run versions I could lay my hands on. Although I'd gotten
> through a manual "make check-world" with this configuration in HEAD
> before touching the buildfarm configuration, I see that it just fell
> over in the back branches. So there's still some more fixing to be
> done, or else we'll need to change that claim again. Will investigate
> once the buildfarm run finishes.

The reason it works manually and not in the buildfarm is that the
buildfarm injects

my $pflags = "PROVE_FLAGS=--timer";

(run_build.pl:1609) and it turns out that 5.8.3's version of prove
does not have the --timer switch. I see that --timer is there in
the next oldest version I have at hand, 5.8.6. I doubt it is worth
teaching the buildfarm scripts to autoconfigure this, but could we
do something like

my $pflags = "PROVE_FLAGS='" . ($ENV{PROVE_FLAGS} || "--timer") . "'";

to allow overriding this choice from the buildfarm config?

FYI, I plan to keep the TAP tests enabled on prairiedog for HEAD,
but probably not for the back branches after this run cycle
finishes, because it's just too-darn-slow.

regards, tom lane