#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my (%HoAoH, $page, %H);

while (<DATA>){
  chomp;
  if (/^Page/){
    (undef, $page) = split /\s+=\s+/;
  }
  elsif (/^\[Start]/){
    %H = ();
  }
  elsif (/^\[End]/){
    push @{$HoAoH{$page}}, {%H};
  }
  else{
    my ($key, $value) = split /\s+=\s+/;

    # updated to produce output suitable for HTML::Template
    #if ($key eq 'varname'){
    #  $varname = $value;
    #}
    #elsif ($key eq 'varval'){
    #  push @AoH, {$varname => $value};
    #}

    $H{$key} = $value;
  }
}
print Dumper(\%HoAoH);

my @page2 = $HoAoH{'second page'};

__DATA__
Page = first page
[Start]
varname = name1
varval = val1
[End]
[Start]
varname = name2
varval = val2
[End]
Page = second page
[Start]
varname = name11
varval = val11
[End]
[Start]
varname = name21
varval = val21
[End]
[download]

output:

---------- Capture Output ----------
> "C:\Perl\bin\perl.exe" sara.pl
$VAR1 = {
          'second page' => [
                             {
                               'varname' => 'name11',
                               'varval' => 'val11'
                             },
                             {
                               'varname' => 'name21',
                               'varval' => 'val21'
                             }
                           ],
          'first page' => [
                            {
                              'varname' => 'name1',
                              'varval' => 'val1'
                            },
                            {
                              'varname' => 'name2',
                              'varval' => 'val2'
                            }
                          ]
        };

> Terminated with exit code 0.
[download]

As CountZero suggested, something like CGI::Session will help you keep track of which page you need to send.

The idea is that you would store the data in a 'session' on the server. You would also store which page was sent. The next time the script is called you'll know which page is needed. CGI::S will do all this for you!

Have a look at it and let us know how you get on.

Good luck!

Update:
It really is a good idea to use strict and warnings as I have (it will make life a lot easier).
Also notice Data::Dumper. If your dealing with data structures like this your life will be twice as easy!
Update 2:
Added how get page2 to the code
Update 3:
Changed structure to suit HTML::Template