template(3)

NAME

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

SYNOPSIS

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:
  <html>
  <head><title>Test Template</title>
  <body>
  My Home Directory is <TMPL_VAR NAME=HOME>
  <p>
  My Path is set to <TMPL_VAR NAME=PATH>
  </body>
  </html>
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/html0, $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

DESCRIPTION

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

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

TUTORIAL

If you're new to HTML::Template, I suggest you start with the introductory article available on the HTML::Template website:: http://html-template.sourceforge.net

MOTIVATION

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 impor
tant 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 exist
ing HTML editors/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

TMPL_VAR: <TMPL_VAR NAME="PARAMETER_NAME">
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 output.
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 ", <, > and & 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 ES; CAPE=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='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'.
TMPL_LOOP: <TMPL_LOOP NAME="LOOP_NAME"> ... </TMPL_LOOP>
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 pro duces output from the text block for each pass. Unset parameters are skipped. Here's an example:: In the template:

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

</TMPL_LOOP>; 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 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

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

# the crucial step - push a reference to this row in

to 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:: <TMPL_LOOP NAME="THIS_LOOP">
Word: <TMPL_VAR NAME="WORD"> <br>
Number: <TMPL_VAR NAME="NUMBER"> <p>; </TMPL_LOOP>
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 visible within a template loop. For the computer-science geeks among you, a <TMPL_LOOP> intro duces 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: <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 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 con sulted. 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.
TMPL_IF: <TMPL_IF NAME="PARAMETER_NAME"> ... </TMPL_IF>
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!; </TMPL_IF>
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.: Not going to work:
<TMPL_IF BOOL>
<TMPL_LOOP SOME_LOOP>; </TMPL_IF>
</TMPL_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
ple:

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

</TMPL_IF>

<TMPL_LOOP LOOP_ONE>

....

</TMPL_LOOP>; 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.; TMPL_ELSE

<TMPL_IF NAME="PARAMETER_NAME"> ... <TMPL_ELSE> ...

</TMPL_IF>; 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>!

Example:

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

<TMPL_ELSE>

Some text that is included only if BOOL is false

</TMPL_IF>; TMPL_UNLESS

<TMPL_UNLESS NAME="PARAMETER_NAME"> ... </TMPL_UNLESS>; 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>.

Example:

<TMPL_UNLESS BOOL>
Some text that is output only if BOOL is FALSE.

<TMPL_ELSE>

Some text that is output only if BOOL is TRUE.

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

<TMPL_UNLESS LOOP_ONE>
This will output if the loop is empty.

</TMPL_UNLESS>

<TMPL_LOOP LOOP_ONE>

....

</TMPL_LOOP>; NOTES; 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 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.

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

METHODS

new()

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_tem; plate_text,
option => 'value'; );
and: my $t = HTML::Template->new( arrayref => $ref_to_ar; ray_of_lines ,
option => 'value'; );
These initialize the template from in-memory resources. In almost every case you'll want to use the filename parameter. If you're worried about all the disk access from reading a template file just use mod_perl and the cache option detailed below.
You can also read the template from an already opened filehandle, either traditionally as a glob or as a File Handle:: my $t = HTML::Template->new( filehandle => *FH, option; => 'value');
The four new() calling methods can also be accessed as below, if you prefer.: my $t = HTML::Template->new_file('file.tmpl', option =>; 'value');; my $t = HTML::Template->new_scalar_ref($ref_to_tem; plate_text,
option => 'val

ue');
my $t = HTML::Template->new_array_ref($ref_to_ar
ray_of_lines,: option => 'value');
my $t = HTML::Template->new_filehandle($fh,: option => 'value');
And as a final option, for those that might prefer it, you can call new as:: my $t = HTML::Template->new(type => 'filename',
source => 'file.tmpl');
Which works for all three of the source types.
If the environment variable HTML_TEMPLATE_ROOT is set and your filename doesn't begin with /, then the path will be relative to the value of $HTML_TEMPLATE_ROOT. Example if the environment variable HTML_TEMPLATE_ROOT is set to "/home/sam" and I call HTML::Template->new() with filename set to "sam.tmpl", the HTML::Template will try to open "/home/sam/sam.tmpl" to access the template file. You can also affect the search path for files with the "path" option to new() - see below for more information.
You can modify the Template object's behavior with new. These 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.; � 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.; � vanguard_compatibility_mode - if set to 1 the mod
ule 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 mem
ory 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
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 bene
fit 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::Shared
Cache 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::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 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 differ
ence between normal caching and shared_cache is
that shared_cache will work in a CGI environment normal caching is only useful in a persistent
environment 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 descrip
tion 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::Shared
Cache.; � 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 caution, 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 test
ing shows that it yields a 50% performance advan
tage. 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) without flock() support is dan
gerous.; � file_cache_dir - sets the directory where the mod
ule 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 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
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 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.
Filesystem Options: � path - you can set this variable with a list of
paths to search for files specified with the
"filename" option to new() and for files included
with the <TMPL_INCLUDE> tag. This list is only
consulted when the filename is relative. The
HTML_TEMPLATE_ROOT environment variable is always
tried first if it exists. In the case of a
<TMPL_INCLUDE> file, the path to the including
file is also tried before path is consulted.

Example:

my $template = HTML::Template->new( filename =>

'file.tmpl',
path => [

'/path/to/templates',
'/al

ternate/path'

]

);
NOTE: the paths in the path list must be expressed as UNIX paths, separated by the forward-slash character ('/').
� search_path_on_include - if set to a true value: the module will search from the top of the array
of paths specified by the path option on every
<TMPL_INCLUDE> and use the first matching template
found. The normal behavior is to look only in the
current directory for a template to include.
Defaults to 0.
Debugging Options: � debug - if set to 1 the module will write random
debugging information to STDERR. Defaults to 0.; � 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 CGI.pm 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('Form; Field'));
had been specified for each key/value pair that would be provided by the $cgi->param() method. Parameters you set directly take precedence over associated parameters.
You can specify multiple objects to associate by passing an anonymous array to the associate option. They are searched for parameters in the order they appear:: my $template = HTML::Template->new(filename =>; 'template.tmpl',
associate =>

[$query, $other_obj]);
The old associateCGI() call is still supported, but should be considered obsolete.
NOTE: The parameter names are matched in a caseinsensitve manner. If you have two parameters in a CGI object like 'NAME' and 'Name' one will be chosen randomly by associate. This behavior can be changed by 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_sensi

tive => 1);

$template->param(

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>

<TMPL_IF NAME="__ODD__">

This outputs every other pass, on the odd

passes.

</TMPL_IF>

<TMPL_UNLESS NAME="__ODD__">

This outputs every other pass, on the even

passes.

</TMPL_IF>

<TMPL_IF NAME="__INNER__">

This outputs on passes that are neither

first nor last.

</TMPL_IF>

<TMPL_IF NAME="__LAST__">

This only outputs on the last pass.

<TMPL_IF>

</TMPL_LOOP>; One use of this feature is to provide a "separa
tor" similar in effect to the perl function
join(). Example:

<TMPL_LOOP FRUIT>
<TMPL_IF __LAST__> and </TMPL_IF>
<TMPL_VAR KIND><TMPL_UNLESS __LAST__>, <TM

PL_ELSE>.</TMPL_UNLESS>

</TMPL_LOOP>; 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 message to be dis
played. 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>.; Example:

This is a normal variable: <TMPL_VAR NORMAL>.<P>

<TMPL_LOOP NAME=FROOT_LOOP>
Here it is inside the loop: <TMPL_VAR NOR

MAL><P>

</TMPL_LOOP>; Normally this wouldn't work as expected, since
<TMPL_VAR NORMAL>'s value outside the loop is not
available inside the loop.; The global_vars option also allows you to access
the values of an enclosing loop within an inner
loop. For example, in this loop the inner loop
will have access to the value of OUTER_VAR in the
correct iteration:

<TMPL_LOOP OUTER_LOOP>
OUTER: <TMPL_VAR OUTER_VAR>
<TMPL_LOOP INNER_LOOP>
INNER: <TMPL_VAR INNER_VAR>
INSIDE OUT: <TMPL_VAR OUTER_VAR>

</TMPL_LOOP>

</TMPL_LOOP>

� filter - this option allows you to specify a fil

ter for your template files. A filter is a sub
routine 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 subrou
tine 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 trans
forms 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 fil ter 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 situa tions.: my $template = HTML::Template->new(filename =>; 'zap.tmpl',
filter => {

sub => $filter,
for

mat => '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,
for

mat => 'scalar' },

{ sub

=> remove_spaces,

for

mat => 'array' }

]);
The specified filters will be called for any TMPL_INCLUDEed files just as they are for the main template file.
param()
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 :: $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,

... }
...

]

}; );
clear_params()
Sets all the parameters to undef. Useful internally, if nowhere else!
output()
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 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:: $template->output(print_to => *STDOUT);
The return value is undefined when using the "print_to" option.
query()
This method allow you to get information about the tem plate structure. It can be called in a number of ways. The simplest usage of query is simply to check whether a parameter name exists in the template, using the "name" option:: if ($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_LOOP NAME="EXAMPLE_LOOP">
<TMPL_VAR NAME="BEE">
<TMPL_VAR NAME="BOP">
<TMPL_LOOP NAME="EXAMPLE_INNER_LOOP">
<TMPL_VAR NAME="INNER_BEE">
<TMPL_VAR NAME="INNER_BOP">

</TMPL_LOOP>; </TMPL_LOOP>
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',
'EXAMPLE_IN

NER_LOOP']);
# and finally, this returns ('inner_bee', 'inner_bop') @inner_param_names = $template->query(loop => ['EXAM
PLE_LOOP',: 'EXAM; PLE_INNER_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.

FREQUENTLY ASKED QUESTIONS

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 help?; A: There's a mailing-list for HTML::Template at
htmltmpl@lists.vm.com. Send a blank message to
htmltmpl-subscribe@lists.vm.com to join!
2 Q: Is there a searchable archive for the mailing-list?: A: Yes, thanks to Sean P. Scanlon, there is:

http://bluedot.net/mail/archive/; 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 definitely 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 publically available CVS server. See below for
more information in the PUBLIC CVS 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> intro
duces 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.; 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_Expres
sions_ 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 startup.pl:

use HTML::Template;
use File::Find;

print STDERR "Pre-loading HTML Templates...0;
find(
sub {
return unless /.tmpl$/;
HTML::Template->new(
filename =>

"$File::Find::dir/$_",
cache => 1,

);

},
'/path/to/templates',
'/another/path/to/templates/'

);

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

One potential problem: the "/path/to/templates/" must
be EXACTLY the same path you use when you call
HTML::Template->new(). Otherwise the cache won't know
they're the same file and will load a new copy instead getting a speed increase, you'll double your
memory usage. To find out if this is happening set
cache_debug => 1 in your application code and look for
"CACHE MISS" messages in the logs.; 8 Q: What characters are allowed in TMPL_* NAMEs?

A: Numbers, letters, '.', '/', '+', '-' and '_'.; 9 Q: How can I execute a program from inside my tem
plate?

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('foo.pl')">

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:

http://member.nifty.ne.jp/hip

po2000/perltips/html/template.htm

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

element using HTML::Template?

A: There is much disagreement on this issue. My per
sonal preference is to use CGI.pm's excellent
popup_menu() and scrolling_list() functions to fill in a single <tmpl_var select_foo> variable.

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

It's a balancing act and you have to weigh the pros
and cons on each side. It is certainly possible to
produce a <select> element entirely inside the tem
plate. What you end up with is a rat's nest of loops
and conditionals. Alternately you can give up a cer
tain amount of flexibility in return for vastly sim
plifying your templates. I generally choose the lat
ter.

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

BUGS

I am aware of no bugs - if you find one, join the mailing
list and tell us about it (htmltmpl@lists.vm.com). You
can join the HTML::Template mailing-list by sending a
blank email to htmltmpl-subscribe@lists.vm.com. Of
course, you can still email me directly (sam@tregar.com)
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.

CREDITS

This module was the brain child of my boss, Jesse Erlbaum
( jesse@vm.com ) at Vanguard Media ( http://vm.com ) .
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 <chouser@bluweb.com>
Larry Moore
Todd Larason
Jody Biggs
T.J. Mather
Martin Schroth
Dave Wolfe
uchum
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
Thanks!

WEBSITE

You can find information about HTML::Template and other related modules at:: http://html-template.sourceforge.net

PUBLIC CVS SERVER

HTML::Template now has a publicly accessible CVS server
provided by SourceForge (www.sourceforge.net). You can
access it by going to http://source
forge.net/cvs/?group_id=1075. Give it a try!

AUTHOR

Sam Tregar, sam@tregar.com (you can also find me on the
mailing list at htmltmpl@lists.vm.com - join it by sending
a blank message to htmltmpl-subscribe@lists.vm.com).

LICENSE

HTML::Template : A module for using HTML Templates with
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 war
ranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR 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 Pub
lic License along with this program; if not, write to the Free Soft
ware Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA

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