#!/usr/bin/perl -wT
#
# -T to set taint mode
use strict;
#
# setup ENV for taint mode
#
delete @ENV{qw(IFS CDPATH ENV BASH_ENV)};   
$ENV{PATH}="/bin:/usr/bin";
#
# die unless the process is running with
# an effective uid of 0 (root)
#
die "Must run as root" unless ($> == 0);
#
# explicitly set real uid to 0 (root),
# so that we can switch effective uid at will
#
$<=0;
if ($< != 0) {
    die "Couldn't set real uid to 0: $!\n";
}
if( my $id =getpwnam("http")) {
     # set the effective uid to http's uid     
     $>=$id;
     if ($> != $id) {die "seteuid failed: $!\n"}
     # run the id shell command that lists uid,euid,etc
     system("id");
}
if( my $otherid =getpwnam("nobody")) {
     # reset the effective uid to 0, or you won't be able to
     # set it to nobody's uid
     $>=0;
     $>=$otherid;
     if ($> != $otherid) {die "seteuid failed: $!\n"}
     system("id");
}