discarding root privileges in suid perl

[Brian May <bam@debian.org>]

Hello,

According to "man perlsec", line 300+, the following code should
destroy extra privileges in a suid root perl script:

      debug "5. killed_euid $EUID $UID\n";

      my @temp = ($EUID, $EGID);
      $EUID = $UID;    
      $EGID = $GID;    #      initgroups() also called!

      debug "6. killed_euid $EUID $UID\n";

      # Make sure privs are really gone
      ($EUID, $EGID) = @temp;

      debug "7. killed_euid $EUID $UID\n";

      die "Can't drop privileges"
        unless $UID == $EUID  && $GID eq $EGID;

(debug statements are my own - these just call print).

However, this is the response I get:

5. killed_euid 0 1003
6. killed_euid 1003 1003
7. killed_euid 0 1003
Can't drop privileges at /usr/local/authorisation/global.pm line 79.

line 5 is the original value of EUID and UID, line 6 is the privileges
after they have been dropped, why do they come back again in line 7?

Is the example in the man page wrong?
-- 
Brian May <bam@debian.org>