The new() constructor creates and returns a reference to a new
Template::Parser object. A reference to a hash may be supplied as a
parameter to provide configuration values. These may include:
- START_TAG, END_TAG
The START_TAG and END_TAG options are used to specify character
sequences or regular expressions that mark the start and end of a
template directive. The default values for START_TAG and END_TAG are
'[%' and '%]' respectively, giving us the familiar directive style:
[% example %]
Any Perl regex characters can be used and therefore should be escaped
(or use the Perl 'quotemeta' function) if they are intended to
represent literal characters.
my $parser = Template::Parser->new({
START_TAG => quotemeta('<+'),
END_TAG => quotemeta('+>'),
});
example:
<+ INCLUDE foobar +>
The TAGS directive can also be used to set the START_TAG and END_TAG values
on a per-template file basis.
[% TAGS <+ +> %]
- TAG_STYLE
The TAG_STYLE option can be used to set both START_TAG and END_TAG
according to pre-defined tag styles.
my $parser = Template::Parser->new({
TAG_STYLE => 'star',
});
Available styles are:
template [% ... %] (default)
template1 [% ... %] or %% ... %% (TT version 1)
metatext %% ... %% (Text::MetaText)
star [* ... *] (TT alternate)
php <? ... ?> (PHP)
asp <% ... %> (ASP)
mason <% ... > (HTML::Mason)
html <!-- ... --> (HTML comments)
Any values specified for START_TAG and/or END_TAG will over-ride
those defined by a TAG_STYLE.
The TAGS directive may also be used to set a TAG_STYLE
[% TAGS html %]
<!-- INCLUDE header -->
- PRE_CHOMP, POST_CHOMP
Anything outside a directive tag is considered plain text and is
generally passed through unaltered (but see the INTERPOLATE option).
This includes all whitespace and newlines characters surrounding
directive tags. Directives that don't generate any output will leave
gaps in the output document.
Example:
Foo
[% a = 10 %]
Bar
Output:
Foo
Bar
The PRE_CHOMP and POST_CHOMP options can help to clean up some of this
extraneous whitespace. Both are disabled by default.
my $parser = Template::Parser->new({
PRE_CHOMP => 1,
POST_CHOMP => 1,
});
With PRE_CHOMP set to 1, the newline and whitespace preceding a directive
at the start of a line will be deleted. This has the effect of
concatenating a line that starts with a directive onto the end of the
previous line.
Foo <----------.
|
,---(PRE_CHOMP)----'
|
`-- [% a = 10 %] --.
|
,---(POST_CHOMP)---'
|
`-> Bar
With POST_CHOMP set to 1, any whitespace after a directive up to and
including the newline will be deleted. This has the effect of joining
a line that ends with a directive onto the start of the next line.
If PRE_CHOMP or POST_CHOMP is set to 2, then instead of removing all
the whitespace, the whitespace will be collapsed to a single space.
This is useful for HTML, where (usually) a contiguous block of
whitespace is rendered the same as a single space.
You may use the CHOMP_NONE, CHOMP_ALL, and CHOMP_COLLAPSE constants
from the Template::Constants module to deactivate chomping, remove
all whitespace, or collapse whitespace to a single space.
PRE_CHOMP and POST_CHOMP can be activated for individual directives by
placing a '-' immediately at the start and/or end of the directive.
[% FOREACH user = userlist %]
[%- user -%]
[% END %]
The '-' characters activate both PRE_CHOMP and POST_CHOMP for the one
directive '[%- name -%]'. Thus, the template will be processed as if
written:
[% FOREACH user = userlist %][% user %][% END %]
Note that this is the same as if PRE_CHOMP and POST_CHOMP were set
to CHOMP_ALL; the only way to get the CHOMP_COLLAPSE behavior is
to set PRE_CHOMP or POST_CHOMP accordingly. If PRE_CHOMP or POST_CHOMP
is already set to CHOMP_COLLAPSE, using '-' will give you CHOMP_COLLAPSE
behavior, not CHOMP_ALL behavior.
Similarly, '+' characters can be used to disable PRE_CHOMP or
POST_CHOMP (i.e. leave the whitespace/newline intact) options on a
per-directive basis.
[% FOREACH user = userlist %]
User: [% user +%]
[% END %]
With POST_CHOMP enabled, the above example would be parsed as if written:
[% FOREACH user = userlist %]User: [% user %]
[% END %]
- INTERPOLATE
The INTERPOLATE flag, when set to any true value will cause variable
references in plain text (i.e. not surrounded by START_TAG and END_TAG)
to be recognised and interpolated accordingly.
my $parser = Template::Parser->new({
INTERPOLATE => 1,
});
Variables should be prefixed by a '$' to identify them. Curly braces
can be used in the familiar Perl/shell style to explicitly scope the
variable name where required.
# INTERPOLATE => 0
<a href="http://[% server %]/[% help %]">
<img src="[% images %]/help.gif"></a>
[% myorg.name %]
# INTERPOLATE => 1
<a href="http://$server/$help">
<img src="$images/help.gif"></a>
$myorg.name
# explicit scoping with { }
<img src="$images/${icon.next}.gif">
Note that a limitation in Perl's regex engine restricts the maximum length
of an interpolated template to around 32 kilobytes or possibly less. Files
that exceed this limit in size will typically cause Perl to dump core with
a segmentation fault. If you routinely process templates of this size
then you should disable INTERPOLATE or split the templates in several
smaller files or blocks which can then be joined backed together via
PROCESS or INCLUDE.
- ANYCASE
By default, directive keywords should be expressed in UPPER CASE. The
ANYCASE option can be set to allow directive keywords to be specified
in any case.
# ANYCASE => 0 (default)
[% INCLUDE foobar %] # OK
[% include foobar %] # ERROR
[% include = 10 %] # OK, 'include' is a variable
# ANYCASE => 1
[% INCLUDE foobar %] # OK
[% include foobar %] # OK
[% include = 10 %] # ERROR, 'include' is reserved word
One side-effect of enabling ANYCASE is that you cannot use a variable
of the same name as a reserved word, regardless of case. The reserved
words are currently:
GET CALL SET DEFAULT INSERT INCLUDE PROCESS WRAPPER
IF UNLESS ELSE ELSIF FOR FOREACH WHILE SWITCH CASE
USE PLUGIN FILTER MACRO PERL RAWPERL BLOCK META
TRY THROW CATCH FINAL NEXT LAST BREAK RETURN STOP
CLEAR TO STEP AND OR NOT MOD DIV END
The only lower case reserved words that cannot be used for variables,
regardless of the ANYCASE option, are the operators:
and or not mod div
- V1DOLLAR
In version 1 of the Template Toolkit, an optional leading '$' could be placed
on any template variable and would be silently ignored.
# VERSION 1
[% $foo %] === [% foo %]
[% $hash.$key %] === [% hash.key %]
To interpolate a variable value the '${' ... '}' construct was used.
Typically, one would do this to index into a hash array when the key
value was stored in a variable.
example:
my $vars = {
users => {
aba => { name => 'Alan Aardvark', ... },
abw => { name => 'Andy Wardley', ... },
...
},
uid => 'aba',
...
};
$template->process('user/home.html', $vars)
|| die $template->error(), "\n";
'user/home.html':
[% user = users.${uid} %] # users.aba
Name: [% user.name %] # Alan Aardvark
This was inconsistent with double quoted strings and also the
INTERPOLATE mode, where a leading '$' in text was enough to indicate a
variable for interpolation, and the additional curly braces were used
to delimit variable names where necessary. Note that this use is
consistent with UNIX and Perl conventions, among others.
# double quoted string interpolation
[% name = "$title ${user.name}" %]
# INTERPOLATE = 1
<img src="$images/help.gif"></a>
<img src="$images/${icon.next}.gif">
For version 2, these inconsistencies have been removed and the syntax
clarified. A leading '$' on a variable is now used exclusively to
indicate that the variable name should be interpolated
(e.g. subsituted for its value) before being used. The earlier example
from version 1:
# VERSION 1
[% user = users.${uid} %]
Name: [% user.name %]
can now be simplified in version 2 as:
# VERSION 2
[% user = users.$uid %]
Name: [% user.name %]
The leading dollar is no longer ignored and has the same effect of
interpolation as '${' ... '}' in version 1. The curly braces may
still be used to explicitly scope the interpolated variable name
where necessary.
e.g.
[% user = users.${me.id} %]
Name: [% user.name %]
The rule applies for all variables, both within directives and in
plain text if processed with the INTERPOLATE option. This means that
you should no longer (if you ever did) add a leading '$' to a variable
inside a directive, unless you explicitly want it to be interpolated.
One obvious side-effect is that any version 1 templates with variables
using a leading '$' will no longer be processed as expected. Given
the following variable definitions,
[% foo = 'bar'
bar = 'baz'
%]
version 1 would interpret the following as:
# VERSION 1
[% $foo %] => [% GET foo %] => bar
whereas version 2 interprets it as:
# VERSION 2
[% $foo %] => [% GET $foo %] => [% GET bar %] => baz
In version 1, the '$' is ignored and the value for the variable 'foo' is
retrieved and printed. In version 2, the variable '$foo' is first interpolated
to give the variable name 'bar' whose value is then retrieved and printed.
The use of the optional '$' has never been strongly recommended, but
to assist in backwards compatibility with any version 1 templates that
may rely on this "feature", the V1DOLLAR option can be set to 1
(default: 0) to revert the behaviour and have leading '$' characters
ignored.
my $parser = Template::Parser->new({
V1DOLLAR => 1,
});
- GRAMMAR
The GRAMMAR configuration item can be used to specify an alternate
grammar for the parser. This allows a modified or entirely new
template language to be constructed and used by the Template Toolkit.
Source templates are compiled to Perl code by the Template::Parser
using the Template::Grammar (by default) to define the language
structure and semantics. Compiled templates are thus inherently
"compatible" with each other and there is nothing to prevent any
number of different template languages being compiled and used within
the same Template Toolkit processing environment (other than the usual
time and memory constraints).
The Template::Grammar file is constructed from a YACC like grammar
(using Parse::YAPP) and a skeleton module template. These files are
provided, along with a small script to rebuild the grammar, in the
'parser' sub-directory of the distribution. You don't have to know or
worry about these unless you want to hack on the template language or
define your own variant. There is a README file in the same directory
which provides some small guidance but it is assumed that you know
what you're doing if you venture herein. If you grok LALR parsers,
then you should find it comfortably familiar.
By default, an instance of the default Template::Grammar will be
created and used automatically if a GRAMMAR item isn't specified.
use MyOrg::Template::Grammar;
my $parser = Template::Parser->new({
GRAMMAR = MyOrg::Template::Grammar->new();
});
- DEBUG
The DEBUG option can be used to enable various debugging features
of the Template::Parser module.
use Template::Constants qw( :debug );
my $template = Template->new({
DEBUG => DEBUG_PARSER | DEBUG_DIRS,
});
The DEBUG value can include any of the following. Multiple values
should be combined using the logical OR operator, '|'.
- DEBUG_PARSER
This flag causes the Template::Parser to generate
debugging messages that show the Perl code generated by parsing and
compiling each template.
- DEBUG_DIRS
This option causes the Template Toolkit to generate comments
indicating the source file, line and original text of each directive
in the template. These comments are embedded in the template output
using the format defined in the DEBUG_FORMAT configuration item, or a
simple default format if unspecified.
For example, the following template fragment:
Hello World
would generate this output:
## input text line 1 : ##
Hello
## input text line 2 : World ##
World
The parse() method parses the text passed in the first parameter and
returns a reference to a Template::Document object which contains the
compiled representation of the template text. On error, undef is
returned.
