export PATH || (echo "OOPS, this isn't sh. Desperation time. I will feed myself to sh."; sh $0; kill $$)
+# Avoid "warning: jobserver unavailable: using -j1." warnings under GNU make.
+# When gmake -j N spawns a child, it passes
+# MAKEFLAGS=" --jobserver-fds=3,4 -j".
+# in the environment. Also, if make recognises that the child is another
+# make (e.g. it's invoked as $(MAKE) or +command), it keeps open fd's 3
+# and 4 to allow the child process to access the job server. Otherwise,
+# those fd's aren't kept open.
+# In the case where one does 'make -j 16 test_harness', this script is
+# called with MAKEFLAGS set, but fd's 3 and 4 closed. Later when
+# descendents of this script run cpan/ExtUtils-Constant/t/Constant.t
+# which itelf invokes make, the warnings ensue.
+
+unset MAKEFLAGS
+
+
case $# in
0)
echo "runtests tty_flag ..."
cd t
+# If this is run under an old shell that doesn't automatically
+# update PWD, then we must update it. Otherwise, t/io/fs.t gets
+# mixed up about what directory we are in.
+case "$PWD" in
+ '') ;; # Do nothing if it isn't set at all.
+ */t) ;; # Leave it alone if it's properly updated.
+ *) PWD=${PWD}/t; export PWD ;; # Otherwise, fix it.
+esac
+
!NO!SUBS!
## In the following, dollars and backticks do need the extra backslash.