t/run/exit.t Test perl's exit status.
t/run/fresh_perl.t Tests that require a fresh perl.
t/run/locale.t Tests related to locale handling
+t/run/mad.t Test vs MAD environment
t/run/noswitch.t Test aliasing ARGV for other switch tests
t/run/runenv.t Test if perl honors its environment variables.
t/run/script.t See if script invocation works