##

use strict;
use CGI;
use MIME::Base64;

my $q = new CGI;
my $mode = $q->param("mode");
if ($mode eq "form1") { &validateform1; }
elsif ...

##

##

use Storable;

# unpack history from form, and add latest form's settings
my %formhash = %{ thaw(
   decode_base64( $q->param("history"))
                        ) };
foreach $p ($q->params) { $formhash{$p}=$q->param($p}; }

# meat of program

# pack back up.  $template contains template file contents.
my $frozen = encode_base64( freeze \%formhash ); # someone check this pls
$template =~ s/HISTORYBUF/$frozen/;
print $template; # do a "print $q->header" at top