You are viewing the version of this documentation from Perl 5.12.3. View the latest version
$REAL_USER_ID
$UID
$<

The real uid of this process. (Mnemonic: it's the uid you came from, if you're running setuid.) You can change both the real uid and the effective uid at the same time by using POSIX::setuid(). Since changes to $< require a system call, check $! after a change attempt to detect any possible errors.