% my $export = param('export');
% session('export', $export );
<input type=checkbox name=export value=1 title="export" <%= $export ? 'checked' : '' %> >
-% my $timefmt = param('timefmt');
+% my $timefmt = param('timefmt') || session("timefmt");
% session('timefmt', $timefmt );
timefmt: <input name=timefmt value="<%= $timefmt %>" placeholder="%d.%m.%Y %H:%M:%S">