#!/usr/bin/perl

use strict;
use warnings;
use CGI qw/:standard/;

my $q = CGI->new();

my $do_redirect = 1; # for example only

# ... build the entire output into a string
$str = "This is your concatenated HTML doc";

if ($do_redirect) {
  print redirect($url);
}
else {
  print $q->header(), $str;
}