The new() constructor method (implemented by the Template::Base base class) instantiates a new Template object. A reference to a hash array of configuration items may be passed as a parameter.

my $tt = Template->new({
    INCLUDE_PATH => '/usr/local/templates',
    EVAL_PERL    => 1,
}) || die $Template::ERROR, "\n";

A reference to a new Template object is returned, or undef on error. In the latter case, the error message can be retrieved by calling error() as a class method or by examining the $Template::ERROR package variable directly.

my $tt = Template->new(\%config)
    || die Template->error(), "\n";

my $tt = Template->new(\%config)
    || die $Template::ERROR, "\n";

For convenience, configuration items may also be specified as a list of items instead of a hash array reference. These are automatically folded into a hash array by the constructor.

my $tt = Template->new(INCLUDE_PATH => '/tmp', POST_CHOMP => 1)
    || die $Template::ERROR, "\n";

The process() method is called to process a template. The first parameter indicates the input template as one of: a filename relative to INCLUDE_PATH, if defined; a reference to a text string containing the template text; or a file handle reference (e.g. IO::Handle or sub-class) or GLOB (e.g. \*STDIN), from which the template can be read. A reference to a hash array may be passed as the second parameter, containing definitions of template variables.

# filename
$tt->process('welcome.tt2')
    || die $tt->error(), "\n";

# text reference
$text = "[% INCLUDE header %]\nHello world!\n[% INCLUDE footer %]";
$tt->process(\$text)
    || die $tt->error(), "\n";

# file handle (GLOB)
$tt->process(\*DATA)
    || die $tt->error(), "\n";

__END__
[% INCLUDE header %]
This is a template defined in the __END__ section which is
accessible via the DATA "file handle".
[% INCLUDE footer %]

By default, the processed template output is printed to STDOUT. The process() method then returns 1 to indicate success. A third parameter may be passed to the process() method to specify a different output location. This value may be one of: a plain string indicating a filename which will be opened (relative to OUTPUT_PATH, if defined) and the output written to; a file GLOB opened ready for output; a reference to a scalar (e.g. a text string) to which output/error is appended; a reference to a subroutine which is called, passing the output as a parameter; or any object reference which implements a print() method (e.g. IO::Handle, Apache::Request, etc.) which will be called, passing the generated output as a parameter.

Examples:

# output filename
$tt->process('welcome.tt2', $vars, 'welcome.html')
    || die $tt->error(), "\n";

# reference to output subroutine
sub myout {
    my $output = shift;
    ...
}
$tt->process('welcome.tt2', $vars, \&myout)
    || die $tt->error(), "\n";

# reference to output text string
my $output = '';
$tt->process('welcome.tt2', $vars, \$output)
    || die $tt->error(), "\n";

print "output: $output\n";

In an Apache/mod_perl handler:

sub handler {
    my $req = shift;

    # ...your code here...

    # direct output to Apache::Request via $req->print($output)
    $tt->process($file, $vars, $req) || do {
        $req->log_reason($tt->error());
        return SERVER_ERROR;
    };
    return OK;
}

After the optional third output argument can come an optional reference to a hash or a list of (name, value) pairs providing further options for the output. The only option currently supported is binmode which, when set to any true value will ensure that files created (but not any existing file handles passed) will be set to binary mode.

# either: hash reference of options
$tt->process($infile, $vars, $outfile, { binmode => 1 })
    || die $tt->error(), "\n";

# or: list of name, value pairs
$tt->process($infile, $vars, $outfile, binmode => 1)
    || die $tt->error(), "\n";

Alternately, the binmode argument can specify a particular IO layer such as :utf8.

$tt->process($infile, $vars, $outfile, binmode => ':utf8')
    || die $tt->error(), "\n";

The OUTPUT configuration item can be used to specify a default output location other than \*STDOUT. The OUTPUT_PATH specifies a directory which should be prefixed to all output locations specified as filenames.

my $tt = Template->new({
    OUTPUT      => sub { ... },       # default
    OUTPUT_PATH => '/tmp',
...
}) || die Template->error(), "\n";

# use default OUTPUT (sub is called)
$tt->process('welcome.tt2', $vars)
    || die $tt->error(), "\n";

# write file to '/tmp/welcome.html'
$tt->process('welcome.tt2', $vars, 'welcome.html')
    || die $tt->error(), "\n";

The process() method returns 1 on success or undef on error. The error message generated in the latter case can be retrieved by calling the error() method. See also CONFIGURATION SUMMARY which describes how error handling may be further customised.

When called as a class method, it returns the value of the $ERROR package variable. Thus, the following are equivalent.

my $tt = Template->new()
    || die Template->error(), "\n";

my $tt = Template->new()
    || die $Template::ERROR, "\n";

When called as an object method, it returns the value of the internal _ERROR variable, as set by an error condition in a previous call to process().

$tt->process('welcome.tt2')
    || die $tt->error(), "\n";

Errors are represented in the Template Toolkit by objects of the Template::Exception class. If the process() method returns a false value then the error() method can be called to return an object of this class. The type() and info() methods can called on the object to retrieve the error type and information string, respectively. The as_string() method can be called to return a string of the form $type - $info. This method is also overloaded onto the stringification operator allowing the object reference itself to be printed to return the formatted error string.

$tt->process('somefile') || do {
    my $error = $tt->error();
    print "error type: ", $error->type(), "\n";
    print "error info: ", $error->info(), "\n";
    print $error, "\n";
};

The Template module delegates most of the effort of processing templates to an underlying Template::Service object. This method returns a reference to that object.

The Template::Service module uses a core Template::Context object for runtime processing of templates. This method returns a reference to that object and is equivalent to $template->service->context().

This method is a simple wrapper around the Template::Context method of the same name. It returns a compiled template for the source provided as an argument.

START_TAG, END_TAG

Define tokens that indicate start and end of directives (default: '[%' and '%]').

TAG_STYLE

Set START_TAG and END_TAG according to a pre-defined style (default: 'template', as above).

PRE_CHOMP, POST_CHOMP

Removes whitespace before/after directives (default: 0/0).

TRIM

Remove leading and trailing whitespace from template output (default: 0).

INTERPOLATE

Interpolate variables embedded like $this or ${this} (default: 0).

ANYCASE

Allow directive keywords in lower case (default: 0 - UPPER only).

INCLUDE_PATH

One or more directories to search for templates.

DELIMITER

Delimiter for separating paths in INCLUDE_PATH (default: ':').

ABSOLUTE

Allow absolute file names, e.g. /foo/bar.html (default: 0).

RELATIVE

Allow relative filenames, e.g. ../foo/bar.html (default: 0).

DEFAULT

Default template to use when another not found.

BLOCKS

Hash array pre-defining template blocks.

AUTO_RESET

Enabled by default causing BLOCK definitions to be reset each time a template is processed. Disable to allow BLOCK definitions to persist.

RECURSION

Flag to permit recursion into templates (default: 0).

VARIABLES

Hash array of variables and values to pre-define in the stash.

EVAL_PERL

Flag to indicate if PERL/RAWPERL blocks should be processed (default: 0).

PRE_PROCESS, POST_PROCESS

Name of template(s) to process before/after main template.

PROCESS

Name of template(s) to process instead of main template.

ERROR

Name of error template or reference to hash array mapping error types to templates.

OUTPUT

Default output location or handler.

OUTPUT_PATH

Directory into which output files can be written.

DEBUG

Enable debugging messages.

CACHE_SIZE

Maximum number of compiled templates to cache in memory (default: undef - cache all)

COMPILE_EXT

Filename extension for compiled template files (default: undef - don't compile).

COMPILE_DIR

Root of directory in which compiled template files should be written (default: undef - don't compile).

PLUGINS

Reference to a hash array mapping plugin names to Perl packages.

PLUGIN_BASE

One or more base classes under which plugins may be found.

LOAD_PERL

Flag to indicate regular Perl modules should be loaded if a named plugin can't be found (default: 0).

FILTERS

Hash array mapping filter names to filter subroutines or factories.

LOAD_TEMPLATES

List of template providers.

LOAD_PLUGINS

List of plugin providers.

LOAD_FILTERS

List of filter providers.

TOLERANT

Set providers to tolerate errors as declinations (default: 0).

SERVICE

Reference to a custom service object (default: Template::Service).

CONTEXT

Reference to a custom context object (default: Template::Context).

STASH

Reference to a custom stash object (default: Template::Stash).

PARSER

Reference to a custom parser object (default: Template::Parser).

GRAMMAR

Reference to a custom grammar object (default: Template::Grammar).

Evaluate and print a variable or value.

[%   GET variable %]    # 'GET' keyword is optional
[%       variable %]
[%       hash.key %]
[%         list.n %]
[%     code(args) %]
[% obj.meth(args) %]
[%  "value: $var" %]

As per GET but without printing result (e.g. call code)

[%  CALL variable %]

Assign a values to variables.

[% SET variable = value %]    # 'SET' also optional
[%     variable = other_variable
       variable = 'literal text @ $100'
       variable = "interpolated text: $var"
       list     = [ val, val, val, val, ... ]
       list     = [ val..val ]
       hash     = { var => val, var => val, ... }
%]

Like SET, but variables are only set if currently unset (i.e. have no true value).

[% DEFAULT variable = value %]

Insert a file without any processing performed on the contents.

[% INSERT legalese.txt %]

Process another template file or block and insert the generated output. Any template BLOCKs or variables defined or updated in the PROCESSed template will thereafter be defined in the calling template.

[% PROCESS template %]
[% PROCESS template  var = val, ... %]

Similar to PROCESS, but using a local copy of the current variables. Any template BLOCKs or variables defined in the INCLUDEd template remain local to it.

[% INCLUDE template %]
[% INCLUDE template  var = val, ... %]

The content between the WRAPPER and correspondng END directives is first evaluated, with the output generated being stored in the content variable. The named template is then process as per INCLUDE.

[% WRAPPER layout %]
   Some template markup [% blah %]...
[% END %]

A simple layout template might look something like this:

Your header here...
[% content %]
Your footer here...

Define a named template block for INCLUDE, PROCESS and WRAPPER to use.

[% BLOCK hello %]
   Hello World
[% END %]

[% INCLUDE hello %]

Repeat the enclosed FOREACH ... END block for each value in the list.

[% FOREACH variable IN [ val, val, val ] %]    # either
[% FOREACH variable IN list %]                 # or
   The variable is set to [% variable %]
[% END %]

The block enclosed between WHILE and END block is processed while the specified condition is true.

[% WHILE condition %]
   content
[% END %]

The enclosed block is processed if the condition is true / false.

[% IF condition %]
   content
[% ELSIF condition %]
 content
[% ELSE %]
 content
[% END %]

[% UNLESS condition %]
   content
[% # ELSIF/ELSE as per IF, above %]
   content
[% END %]

Multi-way switch/case statement.

[% SWITCH variable %]
[%   CASE val1 %]
       content
[%   CASE [ val2, val3 ] %]
       content
[%   CASE %]         # or [% CASE DEFAULT %]
       content
[% END %]

Define a named macro.

[% MACRO name <directive> %]
[% MACRO name(arg1, arg2) <directive> %]
...
[% name %]
[% name(val1, val2) %]

Process enclosed FILTER ... END block then pipe through a filter.

[% FILTER name %]                       # either
[% FILTER name( params ) %]             # or
[% FILTER alias = name( params ) %]     # or
   content
[% END %]

Load a plugin module (see Template::<Manual::Plugins), or any regular Perl module when the LOAD_PERL option is set.

[% USE name %]                      # either
[% USE name( params ) %]            # or
[% USE var = name( params ) %]      # or
...
[% name.method %]
[% var.method %]

Evaluate enclosed blocks as Perl code (requires the EVAL_PERL option to be set).

[% PERL %]
 # perl code goes here
 $stash->set('foo', 10);
 print "set 'foo' to ", $stash->get('foo'), "\n";
 print $context->include('footer', { var => $val });
[% END %]

[% RAWPERL %]
   # raw perl code goes here, no magic but fast.
   $output .= 'some output';
[% END %]

Exception handling.

[% TRY %]
 content
   [% THROW type info %]
[% CATCH type %]
 catch content
   [% error.type %] [% error.info %]
[% CATCH %] # or [% CATCH DEFAULT %]
 content
[% FINAL %]
   this block is always processed
[% END %]

Jump straight to the next item in a FOREACH or WHILE loop.

[% NEXT %]

Break out of FOREACH or WHILE loop.

[% LAST %]

Stop processing current template and return to including templates.

[% RETURN %]

Stop processing all templates and return to caller.

[% STOP %]

Define new tag style or characters (default: [% %]).

[% TAGS html %]
[% TAGS <!-- --> %]

Ignored and deleted.

[% # this is a comment to the end of line
   foo = 'bar'
%]

[%# placing the '#' immediately inside the directive
    tag comments out the entire directive
%]