This is a technique I discovered a while ago. It will probably underwhelm a lot of people who may already have been using it for a while. However I've yet to see it explicitly discussed.

I refer to TT2 and CGI.pm's HTML generation methods as yin and yang here because their common uses represent polar opposites in the emphasis on application- vs. presentation centric design. By combinging the two, you can follow presentation centric design and get stickiness for form elements very painlessly.

So much fuss, so very little to show for it:

#!/usr/bin/perl -w
use strict;
use CGI;
use Template

# ...

my $q = CGI->new;

# ...

$template->process("foo.tmpl.html", {
    query      => $q,
    @other_variables,
}) or die $Template::ERROR;
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Now you can achieve sticky form elements simply by using TT2's object access capabilities to say things like

[% query.textfield("name", "J. Random Hacker", 30) %]
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It is nothing earth shattering. But IMO, its usefulness is in fact because of rather than despite that.

Another use might be to implement purely presentation relevant aspects of a web application completely outside the core CGI script - after all, nothing stops you from querying parameter values as in lang = query.param('lang'); in the template. I have used this to retrofit internationalization on a CGI script without touching the Perl code at all.