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Template(3pm)         User Contributed Perl Documentation        Template(3pm)

       HTML::Template - Perl module to use HTML Templates from CGI scripts

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

       Now create a small CGI program:

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

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

         # 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", $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

       This module attempts to make using HTML templates simple and natural.
       It extends standard HTML with a few new HTML-esque tags - <TMPL_VAR>,
       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 vari-
       ables, 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.

       This module is licensed under the GPL.  See the LICENSE section below
       for more details.

       If you're new to HTML::Template, I suggest you start with the introduc-
       tory article available on the HTML::Template website:

       It is true that there are a number of packages out there to do HTML
       templates.  On the one hand you have things like HTML::Embperl which
       allows you freely mix Perl with HTML.  On the other hand lie home-grown
       variable substitution solutions.  Hopefully the module can find a place
       between the two.

       One advantage of this module over a full HTML::Embperl-esque solution
       is that it enforces an important divide - design and programming.  By
       limiting the programmer to just using simple variables and loops in the
       HTML, the template remains accessible to designers and other non-perl
       people.  The use of HTML-esque syntax goes further to make the format
       understandable to others.  In the future this similarity could be used
       to extend existing HTML editors/analyzers to support HTML::Template.

       An advantage of this module over home-grown tag-replacement schemes is
       the support for loops.  In my work I am often called on to produce
       tables of data in html.  Producing them using simplistic HTML templates
       results in CGIs containing lots of HTML since the HTML itself cannot
       represent loops.  The introduction of loop statements in the HTML sim-
       plifies this situation considerably.  The designer can layout a single
       row and the programmer can fill it in as many times as necessary - all
       they must agree on is the parameter names.

       For all that, I think the best thing about this module is that it does
       just one thing and it does it quickly and carefully.  It doesn't try to
       replace Perl and HTML, it just augments them to interact a little bet-
       ter.  And it's pretty fast.



       The <TMPL_VAR> tag is very simple.  For each <TMPL_VAR> tag in the tem-
       plate you call $template->param(PARAMETER_NAME => "VALUE").  When the
       template is output the <TMPL_VAR> is replaced with the VALUE text you
       specified.  If you don't set a parameter it just gets skipped in the

       Optionally you can use the "ESCAPE=HTML" option in the tag to indicate
       that you want the value to be HTML-escaped before being returned from
       output (the old ESCAPE=1 syntax is still supported).  This means that
       the ", <, >, and & characters get translated into &quot;, &lt;, &gt;
       and &amp; respectively.  This is useful when you want to use a TMPL_VAR
       in a context where those characters would cause trouble.  Example:

          <input name=param type=text value="<TMPL_VAR NAME="PARAM">">

       If you called "param()" with a value like sam"my you'll get in trouble
       with HTML's idea of a double-quote.  On the other hand, if you use
       ESCAPE=HTML, like this:

          <input name=param type=text value="<TMPL_VAR ESCAPE=HTML NAME="PARAM">">

       You'll get what you wanted no matter what value happens to be passed in
       for param.  You can also write ESCAPE="HTML", ESCAPE='HTML' and

       "ESCAPE=0" and "ESCAPE=NONE" turn off escaping, which is the default

       There is also the "ESCAPE=URL" option which may be used for VARs that
       populate a URL.  It will do URL escaping, like replacing ' ' with '+'
       and '/' with '%2F'.

       There is also the "ESCAPE=JS" option which may be used for VARs that
       need to be placed within a Javascript string. All \n, \r, ' and " char-
       acters are escaped.

       You can assign a default value to a variable with the DEFAULT
       attribute.  For example, this will output "the devil gave me a taco" if
       the "who" variable is not set.

         The <TMPL_VAR NAME=WHO DEFAULT=devil> gave me a taco.



       The <TMPL_LOOP> tag is a bit more complicated than <TMPL_VAR>.  The
       <TMPL_LOOP> tag allows you to delimit a section of text and give it a
       name.  Inside this named loop you place <TMPL_VAR>s.  Now you pass to
       "param()" a list (an array ref) of parameter assignments (hash refs)
       for this loop.  The loop iterates over the list and produces output
       from the text block for each pass.  Unset parameters are skipped.
       Here's an example:

        In the template:

             Name: <TMPL_VAR NAME=NAME> <br>
             Job:  <TMPL_VAR NAME=JOB>  <p>

        In the script:

          $template->param(EMPLOYEE_INFO => [
                                              { name => 'Sam', job => 'programmer' },
                                              { name => 'Steve', job => 'soda jerk' },
          print $template->output();

        The output in a browser:

          Name: Sam
          Job: programmer

          Name: Steve
          Job: soda jerk

       As you can see above the <TMPL_LOOP> takes a list of variable assign-
       ments and then iterates over the loop body producing output.

       Often you'll want to generate a <TMPL_LOOP>'s contents programmati-
       cally.  Here's an example of how this can be done (many other ways are

          # a couple of arrays of data to put in a loop:
          my @words = qw(I Am Cool);
          my @numbers = qw(1 2 3);

          my @loop_data = ();  # initialize an array to hold your loop

          while (@words and @numbers) {
            my %row_data;  # get a fresh hash for the row data

            # fill in this row
            $row_data{WORD} = shift @words;
            $row_data{NUMBER} = shift @numbers;

            # the crucial step - push a reference to this row into the loop!
            push(@loop_data, \%row_data);

          # finally, assign the loop data to the loop param, again with a
          # reference:
          $template->param(THIS_LOOP => \@loop_data);

       The above example would work with a template like:

             Word: <TMPL_VAR NAME="WORD">     <br>
             Number: <TMPL_VAR NAME="NUMBER"> <p>

       It would produce output like:

          Word: I
          Number: 1

          Word: Am
          Number: 2

          Word: Cool
          Number: 3

       <TMPL_LOOP>s within <TMPL_LOOP>s are fine and work as you would expect.
       If the syntax for the "param()" call has you stumped, here's an example
       of a param call with one nested loop:

         $template->param(LOOP => [
                                   { name => 'Bobby',
                                     nicknames => [
                                                   { name => 'the big bad wolf' },
                                                   { name => 'He-Man' },

       Basically, each <TMPL_LOOP> gets an array reference.  Inside the array
       are any number of hash references.  These hashes contain the
       name=>value pairs for a single pass over the loop template.

       Inside a <TMPL_LOOP>, the only variables that are usable are the ones
       from the <TMPL_LOOP>.  The variables in the outer blocks are not visi-
       ble within a template loop.  For the computer-science geeks among you,
       a <TMPL_LOOP> introduces a new scope much like a perl subroutine call.
       If you want your variables to be global you can use 'global_vars'
       option to new() described below.


         <TMPL_INCLUDE NAME="filename.tmpl">

       This tag includes a template directly into the current template at the
       point where the tag is found.  The included template contents are used
       exactly as if its contents were physically included in the master tem-

       The file specified can be an absolute path (beginning with a '/' under
       Unix, for example).  If it isn't absolute, the path to the enclosing
       file is tried first.  After that the path in the environment variable
       HTML_TEMPLATE_ROOT is tried, if it exists.  Next, the "path" option is
       consulted, first as-is and then with HTML_TEMPLATE_ROOT prepended if
       available.  As a final attempt, the filename is passed to open()
       directly.  See below for more information on HTML_TEMPLATE_ROOT and the
       "path" option to new().

       As a protection against infinitly recursive includes, an arbitary limit
       of 10 levels deep is imposed.  You can alter this limit with the
       "max_includes" option.  See the entry for the "max_includes" option
       below for more details.



       The <TMPL_IF> tag allows you to include or not include a block of the
       template based on the value of a given parameter name.  If the parame-
       ter is given a value that is true for Perl - like '1' - then the block
       is included in the output.  If it is not defined, or given a false
       value - like '0' - then it is skipped.  The parameters are specified
       the same way as with TMPL_VAR.

       Example Template:

          <TMPL_IF NAME="BOOL">
            Some text that only gets displayed if BOOL is true!

       Now if you call $template->param(BOOL => 1) then the above block will
       be included by output.

       <TMPL_IF> </TMPL_IF> blocks can include any valid HTML::Template con-
       struct - VARs and LOOPs and other IF/ELSE blocks.  Note, however, that
       intersecting a <TMPL_IF> and a <TMPL_LOOP> is invalid.

          Not going to work:
          <TMPL_IF BOOL>
             <TMPL_LOOP SOME_LOOP>

       If the name of a TMPL_LOOP is used in a TMPL_IF, the IF block will out-
       put if the loop has at least one row.  Example:

         <TMPL_IF LOOP_ONE>
           This will output if the loop is not empty.


       WARNING: Much of the benefit of HTML::Template is in decoupling your
       Perl and HTML.  If you introduce numerous cases where you have TMPL_IFs
       and matching Perl if()s, you will create a maintenance problem in keep-
       ing the two synchronized.  I suggest you adopt the practice of only
       using TMPL_IF if you can do so without requiring a matching if() in
       your Perl code.



       You can include an alternate block in your TMPL_IF block by using
       TMPL_ELSE.  NOTE: You still end the block with </TMPL_IF>, not


          <TMPL_IF BOOL>
            Some text that is included only if BOOL is true
            Some text that is included only if BOOL is false



       This tag is the opposite of <TMPL_IF>.  The block is output if the CON-
       TROL_PARAMETER is set false or not defined.  You can use <TMPL_ELSE>
       with <TMPL_UNLESS> just as you can with <TMPL_IF>.


           Some text that is output only if BOOL is FALSE.
           Some text that is output only if BOOL is TRUE.

       If the name of a TMPL_LOOP is used in a TMPL_UNLESS, the UNLESS block
       output if the loop has zero rows.

           This will output if the loop is empty.



       HTML::Template's tags are meant to mimic normal HTML tags.  However,
       they are allowed to "break the rules".  Something like:

          <img src="<TMPL_VAR IMAGE_SRC>">

       is not really valid HTML, but it is a perfectly valid use and will work
       as planned.

       The "NAME=" in the tag is optional, although for extensibility's sake I
       recommend using it.  Example - "<TMPL_LOOP LOOP_NAME>" is acceptable.

       If you're a fanatic about valid HTML and would like your templates to
       conform to valid HTML syntax, you may optionally type template tags in
       the form of HTML comments. This may be of use to HTML authors who would
       like to validate their templates' HTML syntax prior to HTML::Template
       processing, or who use DTD-savvy editing tools.

         <!-- TMPL_VAR NAME=PARAM1 -->

       In order to realize a dramatic savings in bandwidth, the standard
       (non-comment) tags will be used throughout this documentation.


       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

         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 wor-
       ried 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

         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

         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_TEM-
       PLATE_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.

           *   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 every-
               thing so you don't accidentally introduce e.g. cross-site-
               scripting (CSS) vulnerabilities. Requires taint mode. Defaults
               to 0.

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

                  <TMPL_HUH NAME=ZUH>

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

           *   vanguard_compatibility_mode - if set to 1 the module will
               expect to see <TMPL_VAR>s that look like %NAME% in addition to
               the standard syntax.  Also sets die_on_bad_params => 0.  If
               you're not at Vanguard Media trying to use an old format tem-
               plate don't worry about this one.  Defaults to 0.

       Caching Options
           *   cache - if set to 1 the module will cache in memory the parsed
               templates based on the filename parameter and modification date
               of the file.  This only applies to templates opened with the
               filename parameter specified, not scalarref or arrayref tem-
               plates.  Caching also looks at the modification times of any
               files included using <TMPL_INCLUDE> tags, but again, only if
               the template is opened with filename parameter.

               This is mainly of use in a persistent environment like
               Apache/mod_perl.  It has absolutely no benefit in a normal CGI
               environment since the script is unloaded from memory after
               every request.  For a cache that does work for normal CGIs see
               the 'shared_cache' option below.

               Note that different new() parameter settings do not cause a
               cache refresh, only a change in the modification time of the
               template will trigger a cache refresh.  For most usages this is
               fine.  My simplistic testing shows that using cache yields a
               90% performance increase under mod_perl.  Cache defaults to 0.

           *   shared_cache - if set to 1 the module will store its cache in
               shared memory using the IPC::SharedCache module (available from
               CPAN).  The effect of this will be to maintain a single shared
               copy of each parsed template for all instances of HTML::Tem-
               plate to use.  This can be a significant reduction in memory
               usage in a multiple server environment.  As an example, on one
               of our systems we use 4MB of template cache and maintain 25
               httpd processes - shared_cache results in saving almost 100MB!
               Of course, some reduction in speed versus normal caching is to
               be expected.  Another difference between normal caching and
               shared_cache is that shared_cache will work in a CGI environ-
               ment - normal caching is only useful in a persistent environ-
               ment like Apache/mod_perl.

               By default HTML::Template uses the IPC key 'TMPL' as a shared
               root segment (0x4c504d54 in hex), but this can be changed by
               setting the 'ipc_key' new() parameter to another 4-character or
               integer key.  Other options can be used to affect the shared
               memory cache correspond to IPC::SharedCache options - ipc_mode,
               ipc_segment_size and ipc_max_size.  See IPC::SharedCache for a
               description of how these work - in most cases you shouldn't
               need to change them from the defaults.

               For more information about the shared memory cache system used
               by HTML::Template see IPC::SharedCache.

           *   double_cache - if set to 1 the module will use a combination of
               shared_cache and normal cache mode for the best possible
               caching.  Of course, it also uses the most memory of all the
               cache modes.  All the same ipc_* options that work with
               shared_cache apply to double_cache as well.  By default dou-
               ble_cache is off.

           *   blind_cache - if set to 1 the module behaves exactly as with
               normal caching but does not check to see if the file has
               changed on each request.  This option should be used with cau-
               tion, but could be of use on high-load servers.  My tests show
               blind_cache performing only 1 to 2 percent faster than cache
               under mod_perl.

               NOTE: Combining this option with shared_cache can result in
               stale templates stuck permanently in shared memory!

           *   file_cache - if set to 1 the module will store its cache in a
               file using the Storable module.  It uses no additional memory,
               and my simplistic testing shows that it yields a 50% perfor-
               mance advantage.  Like shared_cache, it will work in a CGI
               environment. Default is 0.

               If you set this option you must set the "file_cache_dir"
               option.  See below for details.

               NOTE: Storable using flock() to ensure safe access to cache
               files.  Using file_cache on a system or filesystem (NFS) with-
               out flock() support is dangerous.

           *   file_cache_dir - sets the directory where the module will store
               the cache files if file_cache is enabled.  Your script will
               need write permissions to this directory.  You'll also need to
               make sure the sufficient space is available to store the cache

           *   file_cache_dir_mode - sets the file mode for newly created
               file_cache directories and subdirectories.  Defaults to 0700
               for security but this may be inconvenient if you do not have
               access to the account running the webserver.

           *   double_file_cache - if set to 1 the module will use a combina-
               tion of file_cache and normal cache mode for the best possible
               caching.  The file_cache_* options that work with file_cache
               apply to double_file_cache as well.  By default dou-
               ble_file_cache is 0.

       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_TEM-
               PLATE_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 tem-
               plate found.  The normal behavior is to look only in the cur-
               rent 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.

           *   stack_debug - if set to 1 the module will use Data::Dumper to
               print out the contents of the parse_stack to STDERR.  Defaults
               to 0.

           *   cache_debug - if set to 1 the module will send information on
               cache loads, hits and misses to STDERR.  Defaults to 0.

           *   shared_cache_debug - if set to 1 the module will turn on the
               debug option in IPC::SharedCache - see IPC::SharedCache for
               details. Defaults to 0.

           *   memory_debug - if set to 1 the module will send information on
               cache memory usage to STDERR.  Requires the GTop module.
               Defaults to 0.

       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 pro-
               vided 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]);

               The old associateCGI() call is still supported, but should be
               considered obsolete.

               NOTE: The parameter names are matched in a case-insensitve man-
               ner.  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 the following option.

           *   case_sensitive - setting this option to true causes HTML::Tem-
               plate 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.

               NOTE: with case_sensitive and loop_context_vars the special
               loop variables are available in lower-case only.

           *   loop_context_vars - when this parameter is set to true (it is
               false by default) four loop context variables are made avail-
               able 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 avail-
               able when loop context variables are turned on.


                  <TMPL_LOOP NAME="FOO">
                     <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_LOOP FRUIT>
                     <TMPL_IF __last__> and </TMPL_IF>
                     <TMPL_VAR KIND><TMPL_UNLESS __last__>, <TMPL_ELSE>.</TMPL_UNLESS>

               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__.

           *   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 mes-
               sage 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>

                 <TMPL_LOOP NAME=FROOT_LOOP>
                    Here it is inside the loop: <TMPL_VAR NORMAL><P>

               Normally this wouldn't work as expected, since <TMPL_VAR NOR-
               MAL>'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 OUTER_LOOP>
                     OUTER: <TMPL_VAR OUTER_VAR>
                       <TMPL_LOOP INNER_LOOP>
                          INNER: <TMPL_VAR INNER_VAR>
                          INSIDE OUT: <TMPL_VAR OUTER_VAR>

               One side-effect of global-vars is that variables you set with
               param() that might otherwise be ignored when die_on_bad_params
               is off will stick around.  This is necessary to allow inner
               loops to access values set for outer loops that don't directly
               use the value.

               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.

           *   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 recieve 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 receieve 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 tem-


       "param()" can be called in a number of ways

       1) To return a list of parameters in the template :

          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 recieve 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, ... }

       An error occurs if you try to set a value that is tainted if the
       "force_untaint" option is set.


       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, accumlating 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 allow you to get information about the template structure.
       It can be called in a number of ways.  The simplest usage of query is
       simply to check whether a parameter name exists in the template, using
       the "name" option:

         if ($template->query(name => 'foo')) {
           # do something if a varaible of any type
           # named FOO is in the template

       This same usage returns the type of the parameter.  The type is the
       same as the tag minus the leading 'TMPL_'.  So, for example, a TMPL_VAR
       parameter returns 'VAR' from "query()".

         if ($template->query(name => 'foo') eq 'VAR') {
           # do something if FOO exists and is a TMPL_VAR

       Note that the variables associated with TMPL_IFs and TMPL_UNLESSs will
       be identified as 'VAR' unless they are also used in a TMPL_LOOP, in
       which case they will return 'LOOP'.

       "query()" also allows you to get a list of parameters inside a loop
       (and inside loops inside loops).  Example loop:

            <TMPL_VAR NAME="BEE">
            <TMPL_VAR NAME="BOP">
              <TMPL_VAR NAME="INNER_BEE">
              <TMPL_VAR NAME="INNER_BOP">

       And some query calls:

         # returns 'LOOP'
         $type = $template->query(name => 'EXAMPLE_LOOP');

         # returns ('bop', 'bee', 'example_inner_loop')
         @param_names = $template->query(loop => 'EXAMPLE_LOOP');

         # both return 'VAR'
         $type = $template->query(name => ['EXAMPLE_LOOP', 'BEE']);
         $type = $template->query(name => ['EXAMPLE_LOOP', 'BOP']);

         # and this one returns 'LOOP'
         $type = $template->query(name => ['EXAMPLE_LOOP',

         # and finally, this returns ('inner_bee', 'inner_bop')
         @inner_param_names = $template->query(loop => ['EXAMPLE_LOOP',

         # for non existent parameter names you get undef
         # this returns undef.
         $type = $template->query(name => 'DWEAZLE_ZAPPA');

         # calling loop on a non-loop parameter name will cause an error.
         # this dies:
         $type = $template->query(loop => 'DWEAZLE_ZAPPA');

       As you can see above the "loop" option returns a list of parameter
       names and both "name" and "loop" take array refs in order to refer to
       parameters inside loops.  It is an error to use "loop" with a parameter
       that is not a loop.

       Note that all the names are returned in lowercase and the types are

       Just like "param()", "query()" with no arguments returns all the param-
       eter names in the template at the top level.

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

       1   Q: Is there a place to go to discuss HTML::Template and/or get

           A: There's a mailing-list for discussing HTML::Template at
   To join:


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


       2   Q: Is there a searchable archive for the mailing-list?

           A: Yes, you can find an archive of the SourceForge list here:


           For an archive of the old list, setup by Sean P. Scanlon,


       3   Q: I want support for <TMPL_XXX>!  How about it?

           A: 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 defi-
           nitely have a softening effect on potential opponents!

       4   Q: I found a bug, can you fix it?

           A: 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 has a publi-
           cally available Subversion server.  See below for more information
           in the PUBLIC SUBVERSION SERVER section.

       5   Q: <TMPL_VAR>s from the main template aren't working inside a
           <TMPL_LOOP>!  Why?

           A: This is the intended behavior.  <TMPL_LOOP> introduces a sepa-
           rate 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 documenta-
           tion of the 'global_vars' new() option.

       6   Q: Why do you use /[Tt]/ instead of /t/i?  It's so ugly!

           A: Simple - the case-insensitive match switch is very inefficient.
           According to _Mastering_Regular_Expressions_ from O'Reilly Press,
           /[Tt]/ is faster and more space efficient than /t/i - by as much as
           double against long strings.  //i essentially does a lc() on the
           string and keeps a temporary copy in memory.

           When this changes, and it is in the 5.6 development series, I will
           gladly use //i.  Believe me, I realize [Tt] is hideously ugly.

       7   Q: How can I pre-load my templates using cache-mode and mod_perl?

           A: 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

           One potential problem: the "/path/to/templates/" must be EXACTLY
           the same path you use when you call HTML::Template->new().  Other-
           wise 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

       8   Q: What characters are allowed in TMPL_* NAMEs?

           A: Numbers, letters, '.', '/', '+', '-' and '_'.

       9   Q: How can I execute a program from inside my template?

           A: 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 seperate.

           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.

       10  Q: Can I get a copy of these docs in Japanese?

           A: Yes you can.  See Kawai Takanori's translation at:


       11  Q: What's the best way to create a <select> form element using

           A: There is much disagreement on this issue.  My personal prefer-
           ence is to use'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 tem-
           plates.  I generally choose the latter.

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

       I am aware of no bugs - if you find one, join the mailing list and tell
       us about it.  You can join the HTML::Template mailing-list by visiting:

       Of course, you can still email me directly ( with bugs,
       but I reserve the right to forward bug reports to the mailing list.

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

       If you're feeling really adventurous, HTML::Template has a publically
       available Subversion server.  See below for more information in the

       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 pro-
       vided 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


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

       HTML::Template now has a publicly accessible Subversion server provided
       by SourceForge (  You can access it by going to  Give it a try!

       Sam Tregar,

         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

perl v5.8.8                       2007-04-08                     Template(3pm)

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