+if (defined(my $f = $ENV{TEST_OPEN_FIFO})) {
+ open my $fh, '>', $f or die "open($f): $!";
+ say $fh 'hi';
+ close $fh;
+}
+
+END {
+ if (defined(my $f = $ENV{TEST_EXIT_FIFO})) {
+ open my $fh, '>', $f or die "open($f): $!";
+ say $fh "bye from $$";
+ close $fh;
+ }
+}
+
+my $pi_config = $ENV{PI_CONFIG} // 'unset'; # capture ASAP