in reply to $< and setuid: quite different animals?
Try it the other way round (first effective, then real):
$> = $uid;
$< = $uid;
$ sudo strace ./switchback.pl 2>&1 | grep '^setr'
setresuid(-1, 65534, -1) = 0
setreuid(65534, 4294967295) = 0
setresuid(-1, 0, -1) = -1 EPERM (Operation not perm
setreuid(0, 4294967295) = -1 EPERM (Operation not perm
Electric eels were invented at the same time as electricity
Before electricity was invented, electric eels had to stun with gas
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