?history=view1,view2,view3

##</code><code>##

my ($q, %param, @history);
use CGI;
$q = new CGI;
%param = $q->Vars;
if (defined $param{history}) {
  @history = split(',', $param{history});
}

##</code><code>##

push @history, $param{view_page}

##</code><code>##

my $history = join(',', @history);

my $page1url = $q->url(-absolute=>1)
               . '?history='
               . $history&view_page=view1;

my $page2url = $q->url(-absolute=>1)
               . '?history='
               . $history&view_page=view2;