print "real: $<, effective $>\n";
$> = 1000; # drop privileges
print "real: $<, effective $>\n";
{
    # locally regain privileges
    local $> = 0;
    $> == 0 or die "Insufficient privileges, run script as root";
    print "real: $<, effective $>\n";
}
# unprivileged again
print "real: $<, effective $>\n";