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

       Now create a small CGI program:

         use HTML::Template;

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

         # fill in some parameters
             HOME => $ENV{HOME},
             PATH => $ENV{PATH},

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

         # print the template
         print $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>, <TMPL_LOOP>, <TMPL_INCLUDE>,
       <TMPL_IF> and <TMPL_ELSE>.  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 some­
       one else!  Using this module you fill in the values for
       the variables, loops and branches declared in the tem­

       A Japanese translation of the documentation is available

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


       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 substitu­
       tion 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 edi­
       tors/analyzers to support HTML::Template.

       An advantage of this module over home-grown tag-replace­
       ment schemes is the support for loops.  In my work I am
       often called on to produce tables of data in html.  Pro­
       ducing 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 simplifies 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 better.  And it's
       pretty fast.

The Tags

       Note: even though these tags look like HTML they are a
       little different in a couple of ways.  First, they must
       appear entirely on one line.  Second, they're allowed to
       "break the rules".  Something like:


       The "NAME=" in the tag is optional, although for extensi­
       bility'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 option­
       ally 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 pro­
       cessing, 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 the
       rest of this documentation.


       The <TMPL_VAR> tag is very simple.  For each <TMPL_VAR>
       tag in the template you call $template->param(PARAME­
       TER_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:


       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='1'.  Substitute a 0 for the HTML
       and you turn off escaping, which is the default anyway.

       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'.

       The <TMPL_LOOP> tag is a bit more complicated.  The
       <TMPL_LOOP> tag allows you to delimit a section of text
       and give it a name.  Inside the <TMPL_LOOP> you place
       <TMPL_VAR>s.  Now you pass to param() a list (an array
       ref) of parameter assignments (hash refs).  The loop iter­
       ates over this 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> <P>
                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:

          Name: Sam <P>
          Job: programmer <P>
          Name: Steve <P>
          Job: soda jerk <P>

       As you can see above the <TMPL_LOOP> takes a list of vari­
       able assignments and then iterates over the loop body pro­
       ducing output.

       Often you'll want to generate a <TMPL_LOOP>'s contents
       programmatically.  Here's an example of how this can be
       done (many other ways are possible!):

          # 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
            $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

                                 { 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 visible within a template loop.  For
       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 con­
       tents were physically included in the master template.

       The file specified can be a full path - beginning with a
       '/'.  If it isn't a full path, the path to the enclosing
       file is tried first.  After that the path in the environ­
       ment variable HTML_TEMPLATE_ROOT is tried next, if it
       exists.  Next, the "path" new() option is consulted.  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


       The <TMPL_IF> tag allows you to include or not include a
       block of the template based on the value of a given param­
       eter name.  If the parameter 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 speci­
       fied 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 construct - VARs and LOOPs and other
       IF/ELSE blocks.  Note, however, that intersecting a
       <TMPL_IF> and a <TMPL_LOOP> is invalid.

          <TMPL_IF BOOL>
             <TMPL_LOOP SOME_LOOP>

       If the name of a TMPL_LOOP is used in a TMPL_IF, the IF
       block will output if the loop has at least one row.  Exam­

         <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 keeping the two syn­
       chronized.  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_ELSE>!


          <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 out­
       put if the CONTROL_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.




       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.

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

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

                                               option => 'value');

         my $t = HTML::Template->new_array_ref($ref_to_array_of_lines,
                                              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.
       These options are available:

       ·   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.

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

              <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.

       ·   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 speci­
           fied, not scalarref or arrayref templates.  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
           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 modifica­
           tion 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% perfor­
           mance 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 mod­
           ule (available from CPAN).  The effect of this will be
           to maintain a single shared copy of each parsed tem­
           plate for all instances of HTML::Template 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 main­
           tain 25 httpd processes - shared_cache results in sav­
           ing almost 100MB!  Of course, some reduction in speed
           versus normal caching is to be expected.  Another dif­
           ference between normal caching and shared_cache is
           that shared_cache will work in a CGI environment -
           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_seg­
           ment_size and ipc_max_size.  See the IPC::SharedCache
           manpage for a description of how these work - in most
           cases you shouldn't need to change them from the

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

       ·   double_cache - if set to 1 the module will use a com­
           bination 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 double_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 caution, but could be of use on

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

       ·   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% performance 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 filesys­
           tem (NFS) without 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 direc­
           tory.  You'll also need to make sure the sufficient
           space is available to store the cache files.

       ·   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 inconve­
           nient if you do not have access to the account running
           the webserver.

       ·   double_file_cache - if set to 1 the module will use a
           combination 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 double_file_cache is 0.

       ·   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'));

           be provided by the $cgi->param() method.  Parameters
           you set directly take precedence over associated

           You can specify multiple objects to associate by pass­
           ing 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-insen­
           sitve manner.  If you have two parameters in a CGI
           object like 'NAME' and 'Name' one will be chosen ran­
           domly by associate.  This behavior can be changed by
           the following option.

       ·   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.

       ·   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.  Example:

              <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.
                   This outputs on passes that are neither first nor last.

                 <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().  Exam­

              <TMPL_LOOP FRUIT>
                 <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__.

       ·   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.  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

       ·   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.

           imum 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.

       ·   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.

       ·   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.

       ·   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

           In the most simple usage, you simply assign a code
           reference to the filter parameter.  This subroutine
           will recieve a single arguement - 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);

           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".

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

           Using the 'array' format is likely to be more effi­
           cient since this is how HTML::Template stores the tem­
           plate text internally.  This may change in the future.

           You may also have multiple filters.  This allows sim­
           ple filters to be combined for more elaborate func­
           tionality.  To do this you specify an array of fil­
           ters.  The filters are applied in the order they are

              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.

       ·   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 template don't worry
           about this one.  Defaults to 0.

       ·   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 infor­
           mation on cache loads, hits and misses to STDERR.
           Defaults to 0.

       ·   shared_cache_debug - if set to 1 the module will turn

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


       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.
             $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'

             $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
       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 implementa­
       tion of loops.

       You may optionally supply a filehandle to print to auto­
       matically 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"


       This method allow you to get information about the tem­
       plate 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'

         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

         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

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

            <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 uppercase.

       Just like `param()', `query()' with no arguements returns
       all the parameter 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.

       There's a mailing-list for HTML::Template at  Send a blank message to htmltmpl- to join!

       2) 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!

       3) I found a bug, can you fix it?

       That depends.  Did you send me the VERSION of HTML::Tem­
       plate, a test script and a test template?  If so, then
       almost certainly.

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

       4) <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.

       5) Why do you use /[Tt]/ instead of /t/i?  It's so ugly!

       Simple - the case-insensitive match switch is very ineffi­
       cient.  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 tem­
       porary 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.

       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::Tem­
       plate->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

       7) What characters are allowed in TMPL_* NAMEs?

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

       8) 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 seperate.

       But, inevitably some people still want to do it.  At times
       it has even seemed that HTML::Template development might
       split over this issue, so I will attempt a compromise.
       Here is a method you can use to allow your template
       authors to evaluate arbitrary perl scripts from within the

       First, tell all your designers that when they want to run
       a perl script named "" they should use a tag

       Then, have all your programmers call this subroutine
       instead of calling HTML::Template::new directly.  They
       still use the same parameters, but they also get the pro­
       gram execution.

         sub new_template {
           # get the template object
           my $template = HTML::Template->new(@_);

           # find program parameters and fill them in
           my @params = $template->param();
           for my $param (@params) {
              if ($param =~ /^__execute_(.*)__$/) {
                $template->param($param, do($1));

           # return the template object
           return $template;

       The programs called in this way should return a string
       containing their output.  A more complicated subroutine
       could be written to capture STDOUT from the scripts, but
       this one is simple enough to include in the FAQ.  Another
       improvement would be to use query() to enable program exe­
       cution inside loops.

       9) Can I get a copy of these docs in Japanese?

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


       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 sending a
       blank email to  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 demonstrating the problem!

       If you're feeling really adventurous, HTML::Template has a
       publically available CVS server.  See below for more
       information in the PUBLIC CVS SERVER section.
       This module was the brain child of my boss, Jesse Erlbaum
       ( here at Vanguard Media.  The most original
       idea in this module - the <TMPL_LOOP> - was entirely his.

       Fixes, Bug Reports, Optimizations and Ideas have been gen­
       erously 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



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

       Sam Tregar, (you can also find me on the
       mailing list at - join it by sending
       a blank message to


       HTML::Template : A module for using HTML Templates with
       Perl Copyright (C) 2000 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, or

       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
       PURPOSE.  See either 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 USA