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HTML::Template::PerlInterface - perl interface of HTML::Template::Pro


This help is only on perl interface of HTML::Template::Pro. For syntax of html template files you should see "SYNOPSIS" in HTML::Template::SYNTAX.

First you make a template - this is just a normal HTML file with a few extra tags, the simplest being <TMPL_VAR>

For example, test.tmpl:

  <head><title>Test Template</title>
  My Home Directory is <TMPL_VAR NAME=HOME>
  My Path is set to <TMPL_VAR NAME=PATH>

See HTML::Template::SYNTAX for their syntax.

Now create a small CGI program:

  #!/usr/bin/perl -w
  use HTML::Template::Pro;

  # open the html template
  my $template = HTML::Template::Pro->new(
        filename => 'test.tmpl',
        case_sensitive=> 1);

  # fill in some parameters
  $template->param(HOME => $ENV{HOME});
  $template->param(PATH => $ENV{PATH});

  # send the obligatory Content-Type and print the template output
  print "Content-Type: text/html\n\n";

  # print output

  # this would also work.
  # print $template->output();

  # this would also work. It is faster,
  # but (WARNING!) not compatible with original HTML::Template.
  # $template->output();

If all is well in the universe this should show something like this in your browser when visiting the CGI:

  My Home Directory is /home/some/directory
  My Path is set to /bin;/usr/bin

For the best performance it is recommended to use case_sensitive=>1 in new() and print_to=>\*STDOUT in output().

Note that (HTML::Template::Pro version 0.90+) output(), called in void context, also prints to stdout using built-in htmltmplpro C library calls, so the last call "$template->output();" might be, in fact, the fastest way to call output().

IMPORTANT NOTE: you can safely write

  my $template = HTML::Template->new( ... options ...)
        or even
  my $template = HTML::Template::Expr->new( ... options ...)

with HTML::Template::Pro, because in absence of original HTML::Template and HTML::Template::Expr HTML::Template::Pro intercepts their calls.

You can also use all three modules and safely mix their calls (benchmarking may be the only reason for it). In case you want to mix calls to HTML::Template::Expr and HTML::Template::Pro, the only proper usage of their load is

use HTML::Template; use HTML::Template::Expr; use HTML::Template::Pro;

Of course, if you don't plan to mix them (in most cases) it is enough to simply write

use HTML::Template::Pro;

Simply use HTML::Template::Pro, it supports all functions of HTML::Template::Expr.


HTML::Template::Pro is a fast C/perl+XS implementation of HTML::Template and HTML::Template::Expr. See HTML::Template::Pro for details.

It fully supports template language of HTML::Template as described in HTML::Template::SYNTAX.


"This module attempts to make using HTML templates simple and natural. It extends standard HTML with a few new HTML-esque tags - <TMPL_VAR>, <TMPL_LOOP>, <TMPL_INCLUDE>, <TMPL_IF>, <TMPL_ELSE> and <TMPL_UNLESS>. The file written with HTML and these new tags is called a template. It is usually saved separate from your script - possibly even created by someone else! Using this module you fill in the values for the variables, loops and branches declared in the template. This allows you to separate design - the HTML - from the data, which you generate in the Perl script."

Here is described a perl interface of HTML::Template::Pro and HTML::Template + HTML::Template::Expr. See DISTINCTIONS for brief summary of distinctions between HTML::Template::Pro and HTML::Template.



Call new() to create a new Template object:

  my $template = HTML::Template->new( filename => 'file.tmpl', 
                                      option => 'value' 

You must call new() with at least one name => value pair specifying how to access the template text. You can use filename => 'file.tmpl' to specify a filename to be opened as the template. Alternately you can use:

  my $t = HTML::Template->new( scalarref => $ref_to_template_text, 
                               option => 'value' 


  my $t = HTML::Template->new( arrayref => $ref_to_array_of_lines , 
                               option => 'value' 

These initialize the template from in-memory resources. In almost every case you'll want to use the filename parameter. If you're worried about all the disk access from reading a template file just use mod_perl and the cache option detailed below.

You can also read the template from an already opened filehandle, either traditionally as a glob or as a FileHandle:

  my $t = HTML::Template->new( filehandle => *FH, option => 'value');

The four new() calling methods can also be accessed as below, if you prefer.

  my $t = HTML::Template->new_file('file.tmpl', option => 'value');

  my $t = HTML::Template->new_scalar_ref($ref_to_template_text, 
                                        option => 'value');

  my $t = HTML::Template->new_array_ref($ref_to_array_of_lines, 
                                       option => 'value');

  my $t = HTML::Template->new_filehandle($fh, 
                                       option => 'value');

And as a final option, for those that might prefer it, you can call new as:

  my $t = HTML::Template->new(type => 'filename', 
                              source => 'file.tmpl');

Which works for all three of the source types.

If the environment variable HTML_TEMPLATE_ROOT is set and your filename doesn't begin with /, then the path will be relative to the value of $HTML_TEMPLATE_ROOT. Example - if the environment variable HTML_TEMPLATE_ROOT is set to "/home/sam" and I call HTML::Template->new() with filename set to "sam.tmpl", the HTML::Template will try to open "/home/sam/sam.tmpl" to access the template file. You can also affect the search path for files with the "path" option to new() - see below for more information.

You can modify the Template object's behavior with new(). The options are available:

Error Detection Options
  • die_on_bad_params - if set to 0 the module will let you call $template->param(param_name => 'value') even if 'param_name' doesn't exist in the template body. Defaults to 1 in HTML::Template.

    HTML::Template::Pro always use die_on_bad_params => 0. It currently can't be changed, because HTML::Template::Pro can't know whether a parameter is bad until it finishes output.

    Note that it is wrapper-only option: it is not implemented in the htmltmplpro C library.

  • force_untaint - if set to 1 the module will not allow you to set unescaped parameters with tainted values. If set to 2 you will have to untaint all parameters, including ones with the escape attribute. This option makes sure you untaint everything so you don't accidentally introduce e.g. cross-site-scripting (CSS) vulnerabilities. Requires taint mode. Defaults to 0.

    In the original HTML::Template, if the "force_untaint" option is set an error occurs if you try to set a value that is tainted in the param() call. In HTML::Template::Pro, an error occurs when output is called.

    Note that the tainted value will never be printed; but, to completely suppress output, one should use call to output() that returns string, like print $tmpl->output(); Then output() will die before it returns the string to print.

    Note that it is wrapper-only perl-specific option: it is not implemented in the htmltmplpro C library.

  • strict - if set to 0 the module will allow things that look like they might be TMPL_* tags to get by without dieing. Example:


    Would normally cause an error, but if you call new with strict => 0, HTML::Template will ignore it. Defaults to 1.

    HTML::Template::Pro always implies strict => 0.

Caching Options

HTML::Template use many caching options such as cache, shared_cache, double_cache, blind_cache, file_cache, file_cache_dir, file_cache_dir_mode, double_file_cache to cache preparsed html templates.

Since HTML::Template::Pro parses and outputs templates at once, it silently ignores those options.

Filesystem Options
  • path - you can set this variable with a list of paths to search for files specified with the "filename" option to new() and for files included with the <TMPL_INCLUDE> tag. This list is only consulted when the filename is relative. The HTML_TEMPLATE_ROOT environment variable is always tried first if it exists. Also, if HTML_TEMPLATE_ROOT is set then an attempt will be made to prepend HTML_TEMPLATE_ROOT onto paths in the path array. In the case of a <TMPL_INCLUDE> file, the path to the including file is also tried before path is consulted.


       my $template = HTML::Template->new( filename => 'file.tmpl',
                                           path => [ '/path/to/templates',

    NOTE: the paths in the path list must be expressed as UNIX paths, separated by the forward-slash character ('/').

  • search_path_on_include - if set to a true value the module will search from the top of the array of paths specified by the path option on every <TMPL_INCLUDE> and use the first matching template found. The normal behavior is to look only in the current directory for a template to include. Defaults to 0.

Debugging Options
  • debug - if set to 1 the module will write random debugging information to STDERR. Defaults to 0.

  • HTML::Template use many cache debug options such as stack_debug, cache_debug, shared_cache_debug, memory_debug. Since HTML::Template::Pro parses and outputs templates at once, it silently ignores those options.

Miscellaneous Options
  • associate - this option allows you to inherit the parameter values from other objects. The only requirement for the other object is that it have a param() method that works like HTML::Template's param(). A good candidate would be a query object. Example:

      my $query = new CGI;
      my $template = HTML::Template->new(filename => 'template.tmpl',
                                         associate => $query);

    Now, $template->output() will act as though

      $template->param('FormField', $cgi->param('FormField'));

    had been specified for each key/value pair that would be provided by the $cgi->param() method. Parameters you set directly take precedence over associated parameters.

    You can specify multiple objects to associate by passing an anonymous array to the associate option. They are searched for parameters in the order they appear:

      my $template = HTML::Template->new(filename => 'template.tmpl',
                                         associate => [$query, $other_obj]);

    NOTE: If the option case_sensitive => 0, the parameter names are matched in a case-insensitive manner. If you have two parameters in a CGI object like 'NAME' and 'Name' one will be chosen randomly by associate. This behavior can be changed by setting option case_sensitive to 1.

  • case_sensitive - setting this option to true causes HTML::Template to treat template variable names case-sensitively. The following example would only set one parameter without the "case_sensitive" option:

      my $template = HTML::Template->new(filename => 'template.tmpl',
                                         case_sensitive => 1);
        FieldA => 'foo',
        fIELDa => 'bar',

    This option defaults to off to keep compatibility with HTML::Template. Nevertheless, setting case_sensitive => 1 is encouraged, because it significantly improves performance.

    If case_sensitive is set to 0, the perl wrapper is forced to lowercase keys in every hash it will find in "param" tree, which is sometimes an expensive operation. To avoid this, set case_sensitive => 1.

    If case conversion is necessary, there is an alternative lightweight option tmpl_var_case, which is HTML::Template::Pro specific.

    Note that case_sensitive is wrapper-only option: it is not implemented in the htmltmplpro C library.

  • tmpl_var_case - this option is similar to case_sensitive, but is implemented directly in the htmltmplpro C library. Instead of converting keys in every hash of "param" tree, it converts the name of variable.

    For example, in case of <tmpl_var name="CamelCaseName"> setting tmpl_var_case = ASK_NAME_AS_IS | ASK_NAME_LOWERCASE | ASK_NAME_UPPERCASE will cause HTML::Template::Pro to look into "param" tree for 3 names: CamelCaseName, camelcasename, and CAMELCASENAME.

    By default, the name is asked "as is".

  • loop_context_vars - when this parameter is set to true (it is false by default) four loop context variables are made available inside a loop: __first__, __last__, __inner__, __odd__. They can be used with <TMPL_IF>, <TMPL_UNLESS> and <TMPL_ELSE> to control how a loop is output.

    In addition to the above, a __counter__ var is also made available when loop context variables are turned on.


          <TMPL_IF NAME="__first__">
            This only outputs on the first pass.
          <TMPL_IF NAME="__odd__">
            This outputs every other pass, on the odd passes.
          <TMPL_UNLESS NAME="__odd__">
            This outputs every other pass, on the even passes.
          <TMPL_IF NAME="__inner__">
            This outputs on passes that are neither first nor last.
          This is pass number <TMPL_VAR NAME="__counter__">.
          <TMPL_IF NAME="__last__">
            This only outputs on the last pass.

    One use of this feature is to provide a "separator" similar in effect to the perl function join(). Example:

          <TMPL_IF __last__> and </TMPL_IF>

    Would output (in a browser) something like:

      Apples, Oranges, Brains, Toes, and Kiwi.

    Given an appropriate param() call, of course. NOTE: A loop with only a single pass will get both __first__ and __last__ set to true, but not __inner__.

    NOTE: in the original HTML::Template with case_sensitive = 1 and loop_context_vars the special loop variables are available in lower-case only. In HTML::Template::Pro they are recognized regardless of case.

  • no_includes - set this option to 1 to disallow the <TMPL_INCLUDE> tag in the template file. This can be used to make opening untrusted templates slightly less dangerous. Defaults to 0.

  • max_includes - set this variable to determine the maximum depth that includes can reach. Set to 10 by default. Including files to a depth greater than this value causes an error message to be displayed. Set to 0 to disable this protection.

  • global_vars - normally variables declared outside a loop are not available inside a loop. This option makes <TMPL_VAR>s like global variables in Perl - they have unlimited scope. This option also affects <TMPL_IF> and <TMPL_UNLESS>.


      This is a normal variable: <TMPL_VAR NORMAL>.<P>
         Here it is inside the loop: <TMPL_VAR NORMAL><P>

    Normally this wouldn't work as expected, since <TMPL_VAR NORMAL>'s value outside the loop is not available inside the loop.

    The global_vars option also allows you to access the values of an enclosing loop within an inner loop. For example, in this loop the inner loop will have access to the value of OUTER_VAR in the correct iteration:

            <TMPL_LOOP INNER_LOOP>
               INNER: <TMPL_VAR INNER_VAR>

    NOTE: global_vars is not global_loops (which does not exist). That means that loops you declare at one scope are not available inside other loops even when global_vars is on.

  • path_like_variable_scope - this option switches on a Shigeki Morimoto extension to HTML::Template::Pro that allows access to variables that are outside the current loop scope using path-like expressions.

    Example: {{{ <TMPL_LOOP NAME=class> <TMPL_LOOP NAME=person> <TMPL_VAR NAME="../teacher_name"> <!-- access to class.teacher_name --> <TMPL_VAR NAME="name"> <TMPL_VAR NAME="/top_level_value"> <!-- access to top level value --> <TMPL_VAR NAME="age"> <TMPL_LOOP NAME="../../school"> <!-- enter loop before accessing its vars --> <TMPL_VAR NAME="school_name"> <!-- access to [../../]school.school_name --> </TMPL_LOOP> </TMPL_LOOP> </TMPL_LOOP> }}}

  • filter - this option allows you to specify a filter for your template files. A filter is a subroutine that will be called after HTML::Template reads your template file but before it starts parsing template tags.

    In the most simple usage, you simply assign a code reference to the filter parameter. This subroutine will receive a single argument - a reference to a string containing the template file text. Here is an example that accepts templates with tags that look like "!!!ZAP_VAR FOO!!!" and transforms them into HTML::Template tags:

       my $filter = sub {
         my $text_ref = shift;
         $$text_ref =~ s/!!!ZAP_(.*?)!!!/<TMPL_$1>/g;
       # open zap.tmpl using the above filter
       my $template = HTML::Template->new(filename => 'zap.tmpl',
                                          filter => $filter);

    More complicated usages are possible. You can request that your filter receive the template text as an array of lines rather than as a single scalar. To do that you need to specify your filter using a hash-ref. In this form you specify the filter using the sub key and the desired argument format using the format key. The available formats are scalar and array. Using the array format will incur a performance penalty but may be more convenient in some situations.

       my $template = HTML::Template->new(filename => 'zap.tmpl',
                                          filter => { sub => $filter,
                                                      format => 'array' });

    You may also have multiple filters. This allows simple filters to be combined for more elaborate functionality. To do this you specify an array of filters. The filters are applied in the order they are specified.

       my $template = HTML::Template->new(filename => 'zap.tmpl',
                                          filter => [ 
                                               { sub => \&decompress,
                                                 format => 'scalar' },
                                               { sub => \&remove_spaces,
                                                 format => 'array' }

    The specified filters will be called for any TMPL_INCLUDEed files just as they are for the main template file.

  • default_escape - Set this parameter to "HTML", "URL" or "JS" and HTML::Template will apply the specified escaping to all variables unless they declare a different escape in the template.


param() can be called in a number of ways

1) To return a list of parameters in the template : ( this features is distinct in HTML::Template::Pro: it returns a list of parameters _SET_ after new() )

   my @parameter_names = $self->param();

2) To return the value set to a param :

   my $value = $self->param('PARAM');

3) To set the value of a parameter :

      # For simple TMPL_VARs:
      $self->param(PARAM => 'value');

      # with a subroutine reference that gets called to get the value
      # of the scalar.  The sub will receive the template object as a
      # parameter.
      $self->param(PARAM => sub { return 'value' });   

      # And TMPL_LOOPs:
      $self->param(LOOP_PARAM => 
                    { PARAM => VALUE_FOR_FIRST_PASS, ... }, 
                    { PARAM => VALUE_FOR_SECOND_PASS, ... } 

4) To set the value of a a number of parameters :

     # For simple TMPL_VARs:
     $self->param(PARAM => 'value', 
                  PARAM2 => 'value'

      # And with some TMPL_LOOPs:
      $self->param(PARAM => 'value', 
                   PARAM2 => 'value',
                   LOOP_PARAM => 
                    { PARAM => VALUE_FOR_FIRST_PASS, ... }, 
                    { PARAM => VALUE_FOR_SECOND_PASS, ... } 
                   ANOTHER_LOOP_PARAM => 
                    { PARAM => VALUE_FOR_FIRST_PASS, ... }, 
                    { PARAM => VALUE_FOR_SECOND_PASS, ... } 

5) To set the value of a a number of parameters using a hash-ref :

                      PARAM => 'value', 
                      PARAM2 => 'value',
                      LOOP_PARAM => 
                        { PARAM => VALUE_FOR_FIRST_PASS, ... }, 
                        { PARAM => VALUE_FOR_SECOND_PASS, ... } 
                      ANOTHER_LOOP_PARAM => 
                        { PARAM => VALUE_FOR_FIRST_PASS, ... }, 
                        { PARAM => VALUE_FOR_SECOND_PASS, ... } 


Sets all the parameters to undef. Useful internally, if nowhere else!


output() returns the final result of the template. In most situations you'll want to print this, like:

   print $template->output();

When output is called each occurrence of <TMPL_VAR NAME=name> is replaced with the value assigned to "name" via param(). If a named parameter is unset it is simply replaced with ''. <TMPL_LOOPS> are evaluated once per parameter set, accumulating output on each pass.

Calling output() is guaranteed not to change the state of the Template object, in case you were wondering. This property is mostly important for the internal implementation of loops.

You may optionally supply a filehandle to print to automatically as the template is generated. This may improve performance and lower memory consumption. Example:

   $template->output(print_to => *STDOUT);

The return value is undefined when using the print_to option.


This method is not supported in HTML::Template::Pro.


The main reason for small incompatibilities between HTML::Template and HTML::Template::Pro is the fact that HTML::Template builds parsed tree of template before anything else. So it has an additional information which HTML::Template::Pro obtains during output.

In cases when HTML::Template dies, such as no_includes, bad syntax of template, max_includes and so on, HTML::Template::Pro issues warning to STDERR and continue.


the following options are not supported in HTML::Template::Pro:


The options die_on_bad_params and strict are ignored. HTML::Template::Pro behaves itself as HTML::Template called with die_on_bad_params => 0, strict => 0.

It currently can't be changed, because HTML::Template::Pro can't know whether a parameter is bad before it start output. This may change in future releases.

To keep backward compatibility with HTML::Template, you should explicitly call its new() with die_on_bad_params => 0, strict => 0.


This method is not supported in HTML::Template::Pro.


param() without arguments should return a list of parameters in the template. In HTML::Template::Pro it returns a list of parameters set after new().


With case_sensitive and loop_context_vars the special loop variables should be available in lower-case only.

associate is case_sensitive inside loops.

When submitting bug reports, be sure to include full details, including the VERSION of the module, a test script and a test template demonstrating the problem!


To define a new function, pass a functions option to new:

  $t = HTML::Template::Pro->new(filename => 'foo.tmpl',
                                 functions => 
                                   { func_name => \&func_handler });

  $t = HTML::Template::Expr->new(filename => 'foo.tmpl',
                                 functions => 
                                   { func_name => \&func_handler });

Or, you can use register_function class method to register the function globally:

  HTML::Template::Pro->register_function(func_name => \&func_handler);
  HTML::Template::Expr->register_function(func_name => \&func_handler);

You provide a subroutine reference that will be called during output. It will receive as arguments the parameters specified in the template. For example, here's a function that checks if a directory exists:

  sub directory_exists {
    my $dir_name = shift;
    return 1 if -d $dir_name;
    return 0;

If you call HTML::Template::Expr->new() with a functions arg:

  $t = HTML::Template::Expr->new(filename => 'foo.tmpl',
                                 functions => {
                                    directory_exists => \&directory_exists

Then you can use it in your template:

  <tmpl_if expr="directory_exists('/home/sam')">

This can be abused in ways that make my teeth hurt.

register_function() extended usage (HTML::Template::Pro specific)

register_function() can be called in a number of ways

1) To fetch the names of registered functions in the template:

  • if register_function() was called in a newly created object it returns a

       list of function's that set _after_ or _in_ new():
       my @registered_functions_names = $self->register_function();
  • in global context register_function() will return a list of _ALL_ avalible function's

       my @all_avalible_functions_names =

    2) To fetching the function by name:

       my $function = $self->register_function('FUNCTION_NAME');

    3) To set a new function:

        # Set function, that can be called in templates, wich are processed
        # by the current object:
        $self->register_function(foozicate => sub { ... });
        # Set global function:
        HTML::Template::Pro->register_function(barify    => sub { ... });

for details of "how to defined a function" see in "EXPR: DEFINING NEW FUNCTIONS".


register_function class method can be called in mod_perl's to define widely used common functions to HTML::Template::Expr. Add something like this to your

  use HTML::Template::Pro;

  HTML::Template::Pro->register_function(foozicate => sub { ... });
  HTML::Template::Pro->register_function(barify    => sub { ... });
  HTML::Template::Pro->register_function(baznate   => sub { ... });


HTML::Template::Pro does not forces the HTML::Template global_vars option to be set, whereas currently HTML::Template::Expr does. Anyway, this also will hopefully go away in a future version of HTML::Template::Expr, so if you need global_vars in your templates then you should set it explicitly.


to Sam Tregar,

Original credits of HTML::Template:

This module was the brain child of my boss, Jesse Erlbaum ( ) at Vanguard Media ( ) . The most original idea in this module - the <TMPL_LOOP> - was entirely his.

Fixes, Bug Reports, Optimizations and Ideas have been generously provided by:

   Richard Chen
   Mike Blazer
   Adriano Nagelschmidt Rodrigues
   Andrej Mikus
   Ilya Obshadko
   Kevin Puetz
   Steve Reppucci
   Richard Dice
   Tom Hukins
   Eric Zylberstejn
   David Glasser
   Peter Marelas
   James William Carlson
   Frank D. Cringle
   Winfried Koenig
   Matthew Wickline
   Doug Steinwand
   Drew Taylor
   Tobias Brox
   Michael Lloyd
   Simran Gambhir
   Chris Houser <>
   Larry Moore
   Todd Larason
   Jody Biggs
   T.J. Mather
   Martin Schroth
   Dave Wolfe
   Kawai Takanori
   Peter Guelich
   Chris Nokleberg
   Ralph Corderoy
   William Ward
   Ade Olonoh
   Mark Stosberg
   Lance Thomas
   Roland Giersig
   Jere Julian
   Peter Leonard
   Kenny Smith
   Sean P. Scanlon
   Martin Pfeffer
   David Ferrance
   Gyepi Sam  
   Darren Chamberlain
   Paul Baker
   Gabor Szabo
   Craig Manley
   Richard Fein
   The Phalanx Project
   Sven Neuhaus


Original credits of HTML::Template::Expr:

The following people have generously submitted bug reports, patches and ideas:

   Peter Leonard
   Tatsuhiko Miyagawa



You can find information about HTML::Template::Pro at:

You can find information about HTML::Template and other related modules at:


Sam Tregar, (Main text)

I. Vlasenko, <> (Pecularities of HTML::Template::Pro)


  HTML::Template : A module for using HTML Templates with Perl
  Copyright (C) 2000-2002 Sam Tregar (

  This module is free software; you can redistribute it and/or modify it
  under the terms of either:

  a) the GNU General Public License as published by the Free Software
  Foundation; either version 1, or (at your option) any later version,

  b) the "Artistic License" which comes with this module.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  the GNU General Public License or the Artistic License for more details.

  You should have received a copy of the Artistic License with this
  module, in the file ARTISTIC.  If not, I'll be glad to provide one.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307