#!/usr/bin/perl -wT
use strict;
use CGI qw(:standard);
$| = 1;

my $cgi = new CGI;
my $dir = '/my/httpd/path'; # spoofed
my $old = $ENV{ 'REDIRECT_URL' } || '';
my $new = '';

if ( $old =~ /(.*?)\.foo/i )
  { 
    $new = "$1.bar";
    if ( -e "$dir$new" ) 
    { 
      print redirect( $new );
      exit;
    }
  }
else { doStandard404(); }