I wanted to give the HTML developers a set of variables that they could use. They could pick and choose which of the set they wanted to display. It was a snippet of HTML to display the current weather, so they could show "wind speed", "wind direction", "temperature", "humidity", and so on.... I did something like:

$tmpl = HTML::Template->new('filename' => $TEMPLATE);
$tmpl->param('Temperature' => $current->{'Temperature'});
$tmpl->param('WindDirection' => current->{'WindDirection'});
$tmpl->param('WindSpeed' => $current->{'WindSpeed'});
...
print $tmpl->output();
[download]

and the HTML developers would ideally be able to select from those variables and use them like this:

<TABLE>
<TR>
<TD>
<SPAN CLASS="weather-temp">
<!--TMPL_VAR NAME="Temperature"-->&deg;F
</SPAN>
</TD>
</TR>
</TABLE>
[download]

But actually what I had to do was put ALL the variables into the template, and hide them as a comment, otherwise I would get some error:

<H3>Current weather</H3>
[insert HTML here using a selection of the variables below]

<!--DO NOT REMOVE:<!--TMPL_VAR NAME="Temperature"--><!--TMPL_VAR NAME=
+"PerceivedTemperature"--><!--TMPL_VAR NAME="R
elativeHumidity"--><!--TMPL_VAR NAME="WindDirection"--><!--TMPL_VAR NA
+ME="WindSpeed"--><!--TMPL_VAR NAME="Pressure"
--><!--TMPL_VAR NAME="Visibility"--><!--TMPL_VAR NAME="Icon"--><!--TMP
+L_VAR NAME="IconDescription"-->-->

...
[download]

and I just find that extremely ugly. What's more, if your variables are within a TMPL_LOOP (which I also did a list of news headlines, so in fact I found myself in that situation), then you have to put that blob of commented-out TMPL_VARs inside that loop.

Also I found that somehow this setup was confusing to the HTML designers, so I ended up having to edit the HTML anyway (maybe that's unique to my situation, though), thus smashing my dreams of never having to look at the HTML again.