owner> cat setuid_program
#!/usr/bin/perl -wT

use POSIX;

my $uid  = getuid()  or die "Failed to determine user id.";
my $euid = geteuid() or die "Failed to determine effective user id.";

print "UID = $uid, EUID = $euid.\n";

##</code><code>##

owner> chmod 04755 setuid_program
owner> ls -l setuid_program
-rwsr-xr-x 1 owner owner 202 2007-07-25 18:40 setuid_program
owner> id -u
20375

##</code><code>##

guest> id -u
20244
guest> ./setuid_program 
UID = 20244, EUID = 20244.

##</code><code>##

owner> mount -p
...
/the/device/ - /my/mountpoint nfs - no rw,soft,intr,nosuid,xattr