#!/usr/local/bin/perl
use CGI;                             
$query = new CGI;
print $query->header( -type          => 'text/html', 
                -expires       => '-1d', 
                -Pragma        => 'no-cache', 
                -Cache-control => 'no-cache'
);

# this produces http headers which you could easily roll yourself 
# if you don't wnat to use CGI.pm or CGI::Simple:

use POSIX;

my $expires = POSIX::strftime("%a, %d %b %Y %H:%M:%S GMT", gmtime(time()-24*3600) );
my $now     = POSIX::strftime("%a, %d %b %Y %H:%M:%S GMT", gmtime(time()) );

print "Expires: $expires
Date: $now
Cache-Control: no-cache
Pragma: no-cache
Content-Type: text/html\n\n"

__DATA__
Expires: Fri, 07 Feb 2003 12:11:25 GMT
Date: Sat, 08 Feb 2003 12:11:25 GMT
Cache-Control: no-cache
Pragma: no-cache
Content-Type: text/html; charset=ISO-8859-1