my @data = <DATA>;
my $counter = 0;
my $data;


for(@data){
        if(/^Start/../^End/ && ++$counter){
            $data->{$counter}{$1} = $2 if /^(\w+)=(\w+)/
        }
}

use Data::Dumper;
die Dumper($data);

__END__

output:
$VAR1 = {
          '1' => {
                   'vardesc2' => 'desc2',
                   'varvalue2' => 'value2',
                   'varname2' => 'name2'
                 },
          '0' => {
                   'varname1' => 'name1',
                   'varvalue1' => 'value1',
                   'vardesc1' => 'desc1'
                 },
          '2' => {
                   'varnameN' => 'nameN',
                   'vardescN' => 'descN',
                   'varvalueN' => 'valueN'
                 }
        };
[download]

Looks like you need an AoA (array of arrays) or a AoH (array of hashes) depening on how you want to access the various fields.

You could start by looking at perllol and perldata. When you have a little code to start with and are running into trouble, post another question. You have to do the homework first though.

One way to keep "track of the changes" would be to use CGI::Session.

As has been mentioned, write some code and let us know how you get on.

Good luck!