HTML::Template::FAQ − Frequently Asked Questions about HTML::Template


In the interest of greater understanding I’ve started a FAQ section of the perldocs. Please look in here before you send me email.


Is there a place to go to discuss HTML::Template and/or get help?
There’s a mailing-list for discussing HTML::Template at html−template− Join at:−template−users

If you just want to get email when new releases are available you can join the announcements mailing-list here:−template−announce

Is there a searchable archive for the mailing-list?
Yes, you can find an archive of the SourceForge list here:−template

I want support for < TMPL_XXX >! How about it?
Maybe. I definitely encourage people to discuss their ideas for HTML::Template on the mailing list. Please be ready to explain to me how the new tag fits in with HTML::Template’s mission to provide a fast, lightweight system for using HTML templates.

NOTE: Offering to program said addition and provide it in the form of a patch to the most recent version of HTML::Template will definitely have a softening effect on potential opponents!

I found a bug, can you fix it?
That depends. Did you send me the VERSION of HTML::Template, a test script and a test template? If so, then almost certainly.

If you’re feeling really adventurous, HTML::Template is publicly available on GitHub (−template). Please feel free to fork it and send me a pull request with any changes you have.

< TMPL_VAR >s from the main template aren’t working inside a < TMPL_LOOP >! Why?
This is the intended behavior. "<TMPL_LOOP>" introduces a separate scope for "<TMPL_VAR>s" much like a subroutine call in Perl introduces a separate scope for "my" variables.

If you want your "<TMPL_VAR>"s to be global you can set the "global_vars" option when you call "new()". See above for documentation of the "global_vars" "new()" option.

How can I pre-load my templates using cache-mode and mod_perl?
Add something like this to your

use HTML::Template;
use File::Find;
print STDERR "Pre−loading HTML Templates...\n";
sub {
return unless /\.tmpl$/;
filename => "$File::Find::dir/$_",
cache => 1,

Note that you’ll need to modify the "return unless" line to specify the extension you use for your template files − I use .tmpl, as you can see. You’ll also need to specify the path to your template files.

One potential problem: the /path/to/templates/ must be EXACTLY the same path you use when you call "HTML::Template−>new()". Otherwise the cache won’t know they’re the same file and will load a new copy − instead getting a speed increase, you’ll double your memory usage. To find out if this is happening set "cache_debug =" 1> in your application code and look for " CACHE MISS" messages in the logs.

What characters are allowed in TMPL_* names?
Numbers, letters, ’.’, ’/’, ’+’, ’−’ and ’_’.

How can I execute a program from inside my template?
Short answer: you can’t. Longer answer: you shouldn’t since this violates the fundamental concept behind HTML::Template − that design and code should be separate.

But, inevitably some people still want to do it. If that describes you then you should take a look at HTML::Template::Expr. Using HTML::Template::Expr it should be easy to write a "run_program()" function. Then you can do awful stuff like:

<tmpl_var expr="run_program('')">

Just, please, don’t tell me about it. I’m feeling guilty enough just for writing HTML::Template::Expr in the first place.

What’s the best way to create a <select> form element using HTML::Template?
There is much disagreement on this issue. My personal preference is to use CGI .pm’s excellent "popup_menu()" and "scrolling_list()" functions to fill in a single "<tmpl_var select_foo>" variable.

To some people this smacks of mixing HTML and code in a way that they hoped HTML::Template would help them avoid. To them I’d say that HTML is a violation of the principle of separating design from programming. There’s no clear separation between the programmatic elements of the "<form>" tags and the layout of the "<form>" tags. You’ll have to draw the line somewhere − clearly the designer can’t be entirely in charge of form creation.

It’s a balancing act and you have to weigh the pros and cons on each side. It is certainly possible to produce a "<select>" element entirely inside the template. What you end up with is a rat’s nest of loops and conditionals. Alternately you can give up a certain amount of flexibility in return for vastly simplifying your templates. I generally choose the latter.

Another option is to investigate HTML::FillInForm which some have reported success using to solve this problem.