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my $uid = getpwnam("nobody"); $< = $uid;
$< = $uid; $> = $uid; $> = 0; $< = 0;
$ sudo strace ./switchback 2>&1 | grep '^set' setreuid32(99, -1) = 0 setresuid32(-1, 99, -1) = 0 setresuid32(-1, 0, -1) = 0 setreuid32(0, -1) = 0