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<h1 class="headline">Template::Manual::Directives</h1>
<h2 class="subhead">Template directives</h1>
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<ul class="toc">
<li class=""><a href="#Accessing_and_Updating_Template_Variables">Accessing and Updating Template Variables</a></li>
<li class="sub"><a href="#section_GET">GET</a></li>
<li class="sub"><a href="#section_CALL">CALL</a></li>
<li class="sub"><a href="#section_SET">SET</a></li>
<li class="sub"><a href="#section_DEFAULT">DEFAULT</a></li>
<li class=""><a href="#Processing_Template_Files_and_Blocks">Processing Template Files and Blocks</a></li>
<li class="sub"><a href="#section_INSERT">INSERT</a></li>
<li class="sub"><a href="#section_INCLUDE">INCLUDE</a></li>
<li class="sub"><a href="#section_PROCESS">PROCESS</a></li>
<li class="sub"><a href="#section_WRAPPER">WRAPPER</a></li>
<li class="sub"><a href="#section_BLOCK">BLOCK</a></li>
<li class=""><a href="#Conditional_Processing">Conditional Processing</a></li>
<li class="sub"><a href="#section_IF_UNLESS_ELSIF_ELSE">IF / UNLESS / ELSIF / ELSE</a></li>
<li class="sub"><a href="#section_SWITCH_CASE">SWITCH / CASE</a></li>
<li class=""><a href="#Loop_Processing">Loop Processing</a></li>
<li class="sub"><a href="#section_FOREACH">FOREACH</a></li>
<li class="sub"><a href="#section_WHILE">WHILE</a></li>
<li class=""><a href="#Filters_Plugins_Macros_and_Perl">Filters, Plugins, Macros and Perl</a></li>
<li class="sub"><a href="#section_FILTER">FILTER</a></li>
<li class="sub"><a href="#section_USE">USE</a></li>
<li class="sub"><a href="#section_MACRO">MACRO</a></li>
<li class="sub"><a href="#section_PERL">PERL</a></li>
<li class="sub"><a href="#section_RAWPERL">RAWPERL</a></li>
<li class=""><a href="#Exception_Handling_and_Flow_Control">Exception Handling and Flow Control</a></li>
<li class="sub"><a href="#section_TRY_THROW_CATCH_FINAL">TRY / THROW / CATCH / FINAL</a></li>
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<div class="pod">
<div class="section">
<div class="head">
<h1 id="Accessing_and_Updating_Template_Variables" onclick="switch_section(this)" title="Click title to show/hide section content.">Accessing and Updating Template Variables</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<div class="subsection">
<div class="head">
<h2 id="section_GET" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">GET</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>GET</code> directive retrieves and outputs the value of the
named variable.
</p>
<pre>[% GET foo %]</pre>
<p>
The <code>GET</code> keyword is optional. A variable can be specified in
a directive tag by itself.
</p>
<pre>[% foo %]</pre>
<p>
The variable can have an unlimited number of elements, each separated by
a dot. Each element can have arguments specified within parentheses.
</p>
<pre>[% foo %]
[% bar.baz %]
[% biz.baz(10) %]
...etc...</pre>
<p>
See <a href="../manual/Variables.html">Template::Manual::Variables</a> for a full discussion on template
variables.
</p>
<p>
You can also specify expressions using the logical (<code>and</code>,
<code>or</code>, <code>not</code>, <code>?</code>, <code>:</code>) and
mathematic operators (<code>+</code>, <code>-</code>, <code>*</code>,
<code>/</code>, <code>%</code>, <code>mod</code>, <code>div</code>).
</p>
<pre>[% template.title or default.title %]
[% score * 100 %]
[% order.nitems ? checkout(order.total) : 'no items' %]</pre>
<p>
The <code>div</code> operator returns the integer result of division.
Both <code>%</code> and <code>mod</code> return the modulus (i.e.
remainder) of division.
</p>
<pre>[% 15 / 6 %] # 2.5
[% 15 div 6 %] # 2
[% 15 mod 6 %] # 3</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_CALL" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">CALL</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>CALL</code> directive is similar to <code>GET</code> in
evaluating the variable named, but doesn't print the result returned.
This can be useful when a variable is bound to a sub-routine or object
method which you want to call but aren't interested in the value
returned.
</p>
<pre>[% CALL dbi.disconnect %]
[% CALL inc_page_counter(page_count) %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_SET" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">SET</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>SET</code> directive allows you to assign new values to
existing variables or create new temporary variables.
</p>
<pre>[% SET title = 'Hello World' %]</pre>
<p>
The <code>SET</code> keyword is also optional. [% title = 'Hello World'
%]
</p>
<p>
Variables may be assigned the values of other variables, unquoted numbers
(2.718), literal text ('single quotes') or quoted text ("double quotes").
In the latter case, any variable references within the text will be
interpolated when the string is evaluated. Variables should be prefixed
by <code>$</code>, using curly braces to explicitly scope the variable
name where necessary.
</p>
<pre>[% foo = 'Foo' %] # literal value 'Foo'
[% bar = foo %] # value of variable 'foo'
[% cost = '$100' %] # literal value '$100'
[% item = "$bar: ${cost}.00" %] # value "Foo: $100.00"</pre>
<p>
Multiple variables may be assigned in the same directive and are
evaluated in the order specified. Thus, the above could have been
written:
</p>
<pre>[% foo = 'Foo'
bar = foo
cost = '$100'
item = "$bar: ${cost}.00"
%]</pre>
<p>
Simple expressions can also be used, as per <code>GET</code>.
</p>
<pre>[% ten = 10
twenty = 20
thirty = twenty + ten
forty = 2 * twenty
fifty = 100 div 2
six = twenty mod 7
%]</pre>
<p>
You can concatenate strings together using the <code>' _ '</code>
operator. In Perl 5, the <code>.</code> is used for string concatenation,
but in Perl 6, as in the Template Toolkit, the <code>.</code> will be
used as the method calling operator and <code>' _ '</code> will be used
for string concatenation. Note that the operator must be specified with
surrounding whitespace which, as Larry says, is construed as a feature:
</p>
<pre>[% copyright = '(C) Copyright' _ year _ ' ' _ author %]</pre>
<p>
You can, of course, achieve a similar effect with double quoted string
interpolation.
</p>
<pre>[% copyright = "(C) Copyright $year $author" %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_DEFAULT" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">DEFAULT</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>DEFAULT</code> directive is similar to <code>SET</code> but
only updates variables that are currently undefined or have no "true"
value (in the Perl sense).
</p>
<pre>[% DEFAULT
name = 'John Doe'
id = 'jdoe'
%]</pre>
<p>
This can be particularly useful in common template components to ensure
that some sensible default are provided for otherwise undefined
variables.
</p>
<pre>[% DEFAULT
title = 'Hello World'
bgcol = '#ffffff'
%]
<html>
<head>
<title>[% title %]</title>
</head>
<body bgcolor="[% bgcol %]">
...etc...</pre>
</div>
</div>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Processing_Template_Files_and_Blocks" onclick="switch_section(this)" title="Click title to show/hide section content.">Processing Template Files and Blocks</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<div class="subsection">
<div class="head">
<h2 id="section_INSERT" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">INSERT</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>INSERT</code> directive is used to insert the contents of an
external file at the current position.
</p>
<pre>[% INSERT myfile %]</pre>
<p>
No attempt to parse or process the file is made. The contents, possibly
including any embedded template directives, are inserted intact.
</p>
<p>
The filename specified should be relative to one of the
<code>INCLUDE_PATH</code> directories. Absolute (i.e. starting with
<code>/</code>) and relative (i.e. starting with <code>.</code>)
filenames may be used if the <code>ABSOLUTE</code> and
<code>RELATIVE</code> options are set, respectively. Both these options
are disabled by default.
</p>
<pre>my $template = Template->new({
INCLUDE_PATH => '/here:/there',
});
$template->process('myfile');</pre>
<p>
<i>myfile</i>:
</p>
<pre>[% INSERT foo %] # looks for /here/foo then /there/foo
[% INSERT /etc/passwd %] # file error: ABSOLUTE not set
[% INSERT ../secret %] # file error: RELATIVE not set</pre>
<p>
For convenience, the filename does not need to be quoted as long as it
contains only alphanumeric characters, underscores, dots or forward
slashes. Names containing any other characters should be quoted.
</p>
<pre>[% INSERT misc/legalese.txt %]
[% INSERT 'dos98/Program Files/stupid' %]</pre>
<p>
To evaluate a variable to specify a filename, you should explicitly
prefix it with a <code>$</code> or use double-quoted string
interpolation.
</p>
<pre>[% language = 'en'
legalese = 'misc/legalese.txt'
%]
[% INSERT $legalese %] # misc/legalese.txt
[% INSERT "$language/$legalese" %] # en/misc/legalese.txt</pre>
<p>
Multiple files can be specified using <code>+</code> as a delimiter. All
files should be unquoted names or quoted strings. Any variables should be
interpolated into double-quoted strings.
</p>
<pre>[% INSERT legalese.txt + warning.txt %]
[% INSERT "$legalese" + warning.txt %] # requires quoting</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_INCLUDE" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">INCLUDE</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>INCLUDE</code> directive is used to process and include the
output of another template file or block.
</p>
<pre>[% INCLUDE header %]</pre>
<p>
If a <code>BLOCK</code> of the specified name is defined in the same
file, or in a file from which the current template has been called (i.e.
a parent template) then it will be used in preference to any file of the
same name.
</p>
<pre>[% INCLUDE table %] # uses BLOCK defined below
[% BLOCK table %]
<table>
...
</table>
[% END %]</pre>
<p>
If a <code>BLOCK</code> definition is not currently visible then the
template name should be a file relative to one of the
<code>INCLUDE_PATH</code> directories, or an absolute or relative file
name if the <code>ABSOLUTE</code>/<code>RELATIVE</code> options are
appropriately enabled. The <code>INCLUDE</code> directive automatically
quotes the filename specified, as per <code>INSERT</code> described
above. When a variable contains the name of the template for the
<code>INCLUDE</code> directive, it should be explicitly prefixed by
<code>$</code> or double-quoted
</p>
<pre>[% myheader = 'my/misc/header' %]
[% INCLUDE myheader %] # 'myheader'
[% INCLUDE $myheader %] # 'my/misc/header'
[% INCLUDE "$myheader" %] # 'my/misc/header'</pre>
<p>
Any template directives embedded within the file will be processed
accordingly. All variables currently defined will be visible and
accessible from within the included template.
</p>
<pre>[% title = 'Hello World' %]
[% INCLUDE header %]
<body>
...</pre>
<p>
<i>header</i>:
</p>
<pre><html>
<title>[% title %]</title></pre>
<p>
output:
</p>
<pre><html>
<title>Hello World</title>
<body>
...</pre>
<p>
Local variable definitions may be specified after the template name,
temporarily masking any existing variables. Insignificant whitespace is
ignored within directives so you can add variable definitions on the same
line, the next line or split across several line with comments
interspersed, if you prefer.
</p>
<pre>[% INCLUDE table %]
[% INCLUDE table title="Active Projects" %]
[% INCLUDE table
title = "Active Projects"
bgcolor = "#80ff00" # chartreuse
border = 2
%]</pre>
<p>
The <code>INCLUDE</code> directive localises (i.e. copies) all variables
before processing the template. Any changes made within the included
template will not affect variables in the including template.
</p>
<pre>[% foo = 10 %]
foo is originally [% foo %]
[% INCLUDE bar %]
foo is still [% foo %]
[% BLOCK bar %]
foo was [% foo %]
[% foo = 20 %]
foo is now [% foo %]
[% END %]</pre>
<p>
output:
</p>
<pre>foo is originally 10
foo was 10
foo is now 20
foo is still 10</pre>
<p>
Technical Note: the localisation of the stash (that is, the process by
which variables are copied before an <code>INCLUDE</code> to prevent
being overwritten) is only skin deep. The top-level variable namespace
(hash) is copied, but no attempt is made to perform a deep-copy of other
structures (hashes, arrays, objects, etc.) Therefore, a <code>foo</code>
variable referencing a hash will be copied to create a new
<code>foo</code> variable but which points to the same hash array. Thus,
if you update compound variables (e.g. <code>foo.bar</code>) then you
will change the original copy, regardless of any stash localisation. If
you're not worried about preserving variable values, or you trust the
templates you're including then you might prefer to use the
<code>PROCESS</code> directive which is faster by virtue of not
performing any localisation.
</p>
<p>
You can specify dotted variables as "local" variables to an
<code>INCLUDE</code> directive. However, be aware that because of the
localisation issues explained above (if you skipped the previous
Technical Note above then you might want to go back and read it or skip
this section too), the variables might not actualy be "local". If the
first element of the variable name already references a hash array then
the variable update will affect the original variable.
</p>
<pre>[% foo = {
bar = 'Baz'
}
%]
[% INCLUDE somefile foo.bar='Boz' %]
[% foo.bar %] # Boz</pre>
<p>
This behaviour can be a little unpredictable (and may well be improved
upon in a future version). If you know what you're doing with it and
you're sure that the variables in question are defined (nor not) as you
expect them to be, then you can rely on this feature to implement some
powerful "global" data sharing techniques. Otherwise, you might prefer to
steer well clear and always pass simple (undotted) variables as
parameters to <code>INCLUDE</code> and other similar directives.
</p>
<p>
If you want to process several templates in one go then you can specify
each of their names (quoted or unquoted names only, no unquoted
<code>$variables</code>) joined together by <code>+</code>. The
<code>INCLUDE</code> directive will then process them in order.
</p>
<pre>[% INCLUDE html/header + "site/$header" + site/menu
title = "My Groovy Web Site"
%]</pre>
<p>
The variable stash is localised once and then the templates specified are
processed in order, all within that same variable context. This makes it
slightly faster than specifying several separate <code>INCLUDE</code>
directives (because you only clone the variable stash once instead of n
times), but not quite as "safe" because any variable changes in the first
file will be visible in the second, third and so on. This might be what
you want, of course, but then again, it might not.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_PROCESS" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">PROCESS</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The PROCESS directive is similar to <code>INCLUDE</code> but does not
perform any localisation of variables before processing the template. Any
changes made to variables within the included template will be visible in
the including template.
</p>
<pre>[% foo = 10 %]
foo is [% foo %]
[% PROCESS bar %]
foo is [% foo %]
[% BLOCK bar %]
[% foo = 20 %]
changed foo to [% foo %]
[% END %]</pre>
<p>
output:
</p>
<pre>foo is 10
changed foo to 20
foo is 20</pre>
<p>
Parameters may be specified in the <code>PROCESS</code> directive, but
these too will become visible changes to current variable values.
</p>
<pre>[% foo = 10 %]
foo is [% foo %]
[% PROCESS bar
foo = 20
%]
foo is [% foo %]
[% BLOCK bar %]
this is bar, foo is [% foo %]
[% END %]</pre>
<p>
output:
</p>
<pre>foo is 10
this is bar, foo is 20
foo is 20</pre>
<p>
The <code>PROCESS</code> directive is slightly faster than
<code>INCLUDE</code> because it avoids the need to localise (i.e. copy)
the variable stash before processing the template. As with
<code>INSERT</code> and <code>INCLUDE</code>, the first parameter does
not need to be quoted as long as it contains only alphanumeric
characters, underscores, periods or forward slashes. A <code>$</code>
prefix can be used to explicitly indicate a variable which should be
interpolated to provide the template name:
</p>
<pre>[% myheader = 'my/misc/header' %]
[% PROCESS myheader %] # 'myheader'
[% PROCESS $myheader %] # 'my/misc/header'</pre>
<p>
As with <code>INCLUDE</code>, multiple templates can be specified,
delimited by <code>+</code>, and are processed in order.
</p>
<pre>[% PROCESS html/header + my/header %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_WRAPPER" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">WRAPPER</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
It's not unusual to find yourself adding common headers and footers to
pages or sub-sections within a page. Something like this:
</p>
<pre>[% INCLUDE section/header
title = 'Quantum Mechanics'
%]
Quantum mechanics is a very interesting subject wish
should prove easy for the layman to fully comprehend.
[% INCLUDE section/footer %]
[% INCLUDE section/header
title = 'Desktop Nuclear Fusion for under $50'
%]
This describes a simple device which generates significant
sustainable electrical power from common tap water by process
of nuclear fusion.
[% INCLUDE section/footer %]</pre>
<p>
The individual template components being included might look like these:
</p>
<p>
section/header:
</p>
<pre><p>
<h2>[% title %]</h2></pre>
<p>
section/footer:
</p>
<pre></p></pre>
<p>
The <code>WRAPPER</code> directive provides a way of simplifying this a
little. It encloses a block up to a matching <code>END</code> directive,
which is first processed to generate some output. This is then passed to
the named template file or <code>BLOCK</code> as the <code>content</code>
variable.
</p>
<pre>[% WRAPPER section
title = 'Quantum Mechanics'
%]
Quantum mechanics is a very interesting subject wish
should prove easy for the layman to fully comprehend.
[% END %]
[% WRAPPER section
title = 'Desktop Nuclear Fusion for under $50'
%]
This describes a simple device which generates significant
sustainable electrical power from common tap water by process
of nuclear fusion.
[% END %]</pre>
<p>
The single 'section' template can then be defined as:
</p>
<pre><h2>[% title %]</h2>
<p>
[% content %]
</p></pre>
<p>
Like other block directives, it can be used in side-effect notation:
</p>
<pre>[% INSERT legalese.txt WRAPPER big_bold_table %]</pre>
<p>
It's also possible to specify multiple templates to a
<code>WRAPPER</code> directive. The specification order indicates
outermost to innermost wrapper templates. For example, given the
following template block definitions:
</p>
<pre>[% BLOCK bold %]<b>[% content %]</b>[% END %]
[% BLOCK italic %]<i>[% content %]</i>[% END %]</pre>
<p>
the directive
</p>
<pre>[% WRAPPER bold+italic %]Hello World[% END %]</pre>
<p>
would generate the following output:
</p>
<pre><b><i>Hello World</i></b></pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_BLOCK" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">BLOCK</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>BLOCK</code>...<code>END</code> construct can be used to define
template component blocks which can be processed with the
<code>INCLUDE</code>, <code>PROCESS</code> and <code>WRAPPER</code>
directives.
</p>
<pre>[% BLOCK tabrow %]
<tr>
<td>[% name %]<td>
<td>[% email %]</td>
</tr>
[% END %]
<table>
[% PROCESS tabrow name='Fred' email='fred@nowhere.com' %]
[% PROCESS tabrow name='Alan' email='alan@nowhere.com' %]
</table></pre>
<p>
A <code>BLOCK</code> definition can be used before it is defined, as long
as the definition resides in the same file. The block definition itself
does not generate any output.
</p>
<pre>[% PROCESS tmpblk %]
[% BLOCK tmpblk %] This is OK [% END %]</pre>
<p>
You can use an anonymous <code>BLOCK</code> to capture the output of a
template fragment.
</p>
<pre>[% julius = BLOCK %]
And Caesar's spirit, ranging for revenge,
With Ate by his side come hot from hell,
Shall in these confines with a monarch's voice
Cry 'Havoc', and let slip the dogs of war;
That this foul deed shall smell above the earth
With carrion men, groaning for burial.
[% END %]</pre>
<p>
Like a named block, it can contain any other template directives which
are processed when the block is defined. The output generated by the
block is then assigned to the variable <code>julius</code>.
</p>
<p>
Anonymous <code>BLOCK</code>s can also be used to define block macros.
The enclosing block is processed each time the macro is called.
</p>
<pre>[% MACRO locate BLOCK %]
The [% animal %] sat on the [% place %].
[% END %]
[% locate(animal='cat', place='mat') %] # The cat sat on the mat
[% locate(animal='dog', place='log') %] # The dog sat on the log</pre>
</div>
</div>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Conditional_Processing" onclick="switch_section(this)" title="Click title to show/hide section content.">Conditional Processing</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<div class="subsection">
<div class="head">
<h2 id="section_IF_UNLESS_ELSIF_ELSE" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">IF / UNLESS / ELSIF / ELSE</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>IF</code> and <code>UNLESS</code> directives can be used to
process or ignore a block based on some run-time condition.
</p>
<pre>[% IF frames %]
[% INCLUDE frameset %]
[% END %]
[% UNLESS text_mode %]
[% INCLUDE biglogo %]
[% END %]</pre>
<p>
Multiple conditions may be joined with <code>ELSIF</code> and/or
<code>ELSE</code> blocks.
</p>
<pre>[% IF age < 10 %]
Hello [% name %], does your mother know you're
using her AOL account?
[% ELSIF age < 18 %]
Sorry, you're not old enough to enter
(and too dumb to lie about your age)
[% ELSE %]
Welcome [% name %].
[% END %]</pre>
<p>
The following conditional and boolean operators may be used:
</p>
<pre>== != < <= > >= && || ! and or not</pre>
<p>
Conditions may be arbitrarily complex and are evaluated with the same
precedence as in Perl. Parenthesis may be used to explicitly determine
evaluation order.
</p>
<pre># ridiculously contrived complex example
[% IF (name == 'admin' || uid <= 0) && mode == 'debug' %]
I'm confused.
[% ELSIF more > less %]
That's more or less correct.
[% END %]</pre>
<p>
The <code>and</code>, <code>or</code> and <code>not</code> operator are
provided as aliases for <code>&&</code>, <code>||</code> and
<code>!</code>, respectively. Unlike Perl, which treats <code>and</code>,
<code>or</code> and <code>not</code> as separate, lower-precedence
versions of the other operators, the Template Toolkit performs a
straightforward substitution of <code>and</code> for
<code>&&</code>, and so on. That means that <code>and</code>,
<code>or</code> and <code>not</code> have the same operator precedence as
<code>&&</code>, <code>||</code> and <code>!</code>.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_SWITCH_CASE" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">SWITCH / CASE</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>SWITCH</code> / <code>CASE</code> construct can be used to
perform a multi-way conditional test. The <code>SWITCH</code> directive
expects an expression which is first evaluated and then compared against
each CASE statement in turn. Each <code>CASE</code> directive should
contain a single value or a list of values which should match.
<code>CASE</code> may also be left blank or written as <code>[% CASE
DEFAULT %]</code> to specify a default match. Only one <code>CASE</code>
matches, there is no drop-through between <code>CASE</code> statements.
</p>
<pre>[% SWITCH myvar %]
[% CASE value1 %]
...
[% CASE [ value2 value3 ] %] # multiple values
...
[% CASE myhash.keys %] # ditto
...
[% CASE %] # default
...
[% END %]</pre>
</div>
</div>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Loop_Processing" onclick="switch_section(this)" title="Click title to show/hide section content.">Loop Processing</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<div class="subsection">
<div class="head">
<h2 id="section_FOREACH" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">FOREACH</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>FOREACH</code> directive will iterate through the items in a
list, processing the enclosed block for each one.
</p>
<pre>my $vars = {
foo => 'Foo',
items => [ 'one', 'two', 'three' ],
};
template:</pre>
<pre>Things:
[% FOREACH thing = [ foo 'Bar' "$foo Baz" ] %]
* [% thing %]
[% END %]
Items:
[% FOREACH i IN items %]
* [% i %]
[% END %]
Stuff:
[% stuff = [ foo "$foo Bar" ] %]
[% FOREACH s IN stuff %]
* [% s %]
[% END %]</pre>
<p>
output:
</p>
<pre>Things:
* Foo
* Bar
* Foo Baz
Items:
* one
* two
* three
Stuff:
* Foo
* Foo Bar</pre>
<p>
You can use also use <code>IN</code> instead of <code>=</code> if you
prefer.
</p>
<pre>[% FOREACH crook IN government %]</pre>
<p>
When the <code>FOREACH</code> directive is used without specifying a
target variable, any iterated values which are hash references will be
automatically imported.
</p>
<pre>[% userlist = [
{ id => 'tom', name => 'Thomas' },
{ id => 'dick', name => 'Richard' },
{ id => 'larry', name => 'Lawrence' },
]
%]
[% FOREACH user IN userlist %]
[% user.id %] [% user.name %]
[% END %]</pre>
<p>
short form:
</p>
<pre>[% FOREACH userlist %]
[% id %] [% name %]
[% END %]</pre>
<p>
Note that this particular usage creates a localised variable context to
prevent the imported hash keys from overwriting any existing variables.
The imported definitions and any other variables defined in such a
<code>FOREACH</code> loop will be lost at the end of the loop, when the
previous context and variable values are restored.
</p>
<p>
However, under normal operation, the loop variable remains in scope after
the <code>FOREACH</code> loop has ended (caveat: overwriting any variable
previously in scope). This is useful as the loop variable is secretly an
iterator object (see below) and can be used to analyse the last entry
processed by the loop.
</p>
<p>
The <code>FOREACH</code> directive can also be used to iterate through
the entries in a hash array. Each entry in the hash is returned in sorted
order (based on the key) as a hash array containing 'key' and 'value'
items.
</p>
<pre>[% users = {
tom => 'Thomas',
dick => 'Richard',
larry => 'Lawrence',
}
%]
[% FOREACH u IN users %]
* [% u.key %] : [% u.value %]
[% END %]</pre>
<p>
Output:
</p>
<pre>* dick : Richard
* larry : Lawrence
* tom : Thomas </pre>
<p>
The <code>NEXT</code> directive starts the next iteration in the
<code>FOREACH</code> loop.
</p>
<pre>[% FOREACH user IN userlist %]
[% NEXT IF user.isguest %]
Name: [% user.name %] Email: [% user.email %]
[% END %]</pre>
<p>
The <code>LAST</code> directive can be used to prematurely exit the loop.
<code>BREAK</code> is also provided as an alias for <code>LAST</code>.
</p>
<pre>[% FOREACH match IN results.nsort('score').reverse %]
[% LAST IF match.score < 50 %]
[% match.score %] : [% match.url %]
[% END %]</pre>
<p>
The <code>FOREACH</code> directive is implemented using the <a href="../modules/Template/Iterator.html">Template::Iterator</a> module. A
reference to the iterator object for a <code>FOREACH</code> directive is
implicitly available in the <code>loop</code> variable. The following
methods can be called on the <code>loop</code> iterator.
</p>
<pre>size() number of elements in the list
max() index number of last element (size - 1)
index() index of current iteration from 0 to max()
count() iteration counter from 1 to size() (i.e. index() + 1)
first() true if the current iteration is the first
last() true if the current iteration is the last
prev() return the previous item in the list
next() return the next item in the list</pre>
<p>
See <a href="../modules/Template/Iterator.html">Template::Iterator</a> for further details.
</p>
<p>
Example:
</p>
<pre>[% FOREACH item IN [ 'foo', 'bar', 'baz' ] -%]
[%- "<ul>\n" IF loop.first %]
<li>[% loop.count %]/[% loop.size %]: [% item %]
[%- "</ul>\n" IF loop.last %]
[% END %]</pre>
<p>
Output:
</p>
<pre><ul>
<li>1/3: foo
<li>2/3: bar
<li>3/3: baz
</ul></pre>
<p>
Nested loops will work as expected, with the <code>loop</code> variable
correctly referencing the innermost loop and being restored to any
previous value (i.e. an outer loop) at the end of the loop.
</p>
<pre>[% FOREACH group IN grouplist;
# loop => group iterator
"Groups:\n" IF loop.first;
FOREACH user IN group.userlist;
# loop => user iterator
"$loop.count: $user.name\n";
END;
# loop => group iterator
"End of Groups\n" IF loop.last;
END
%]</pre>
<p>
The <code>iterator</code> plugin can also be used to explicitly create an
iterator object. This can be useful within nested loops where you need to
keep a reference to the outer iterator within the inner loop. The
iterator plugin effectively allows you to create an iterator by a name
other than <code>loop</code>. See <a href="../modules/Template/Plugin/Iterator.html">Template::Plugin::Iterator</a> for further details.
</p>
<pre>[% USE giter = iterator(grouplist) %]
[% FOREACH group IN giter %]
[% FOREACH user IN group.userlist %]
user #[% loop.count %] in
group [% giter.count %] is
named [% user.name %]
[% END %]
[% END %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_WHILE" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">WHILE</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>WHILE</code> directive can be used to repeatedly process a
template block while a conditional expression evaluates true. The
expression may be arbitrarily complex as per <code>IF</code> /
<code>UNLESS</code>.
</p>
<pre>[% WHILE total < 100 %]
...
[% total = calculate_new_total %]
[% END %]</pre>
<p>
An assignment can be enclosed in parenthesis to evaluate the assigned
value.
</p>
<pre>[% WHILE (user = get_next_user_record) %]
[% user.name %]
[% END %]</pre>
<p>
The <code>NEXT</code> directive can be used to start the next iteration
of a <code>WHILE</code> loop and <code>BREAK</code> can be used to exit
the loop, both as per <code>FOREACH</code>.
</p>
<p>
The Template Toolkit uses a failsafe counter to prevent runaway
<code>WHILE</code> loops which would otherwise never terminate. If the
loop exceeds 1000 iterations then an <code>undef</code> exception will be
thrown, reporting the error:
</p>
<pre>WHILE loop terminated (> 1000 iterations)</pre>
<p>
The <code>$Template::Directive::WHILE_MAX</code> variable controls this
behaviour and can be set to a higher value if necessary.
</p>
</div>
</div>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Filters_Plugins_Macros_and_Perl" onclick="switch_section(this)" title="Click title to show/hide section content.">Filters, Plugins, Macros and Perl</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<div class="subsection">
<div class="head">
<h2 id="section_FILTER" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">FILTER</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>FILTER</code> directive can be used to post-process the output
of a block. A number of standard filters are provided with the Template
Toolkit. The <code>html</code> filter, for example, escapes the '<',
'>' and '&' characters to prevent them from being interpreted as
HTML tags or entity reference markers.
</p>
<pre>[% FILTER html %]
HTML text may have < and > characters embedded
which you want converted to the correct HTML entities.
[% END %]</pre>
<p>
output:
</p>
<pre>HTML text may have &lt; and &gt; characters embedded
which you want converted to the correct HTML entities.</pre>
<p>
The <code>FILTER</code> directive can also follow various other non-block
directives. For example:
</p>
<pre>[% INCLUDE mytext FILTER html %]</pre>
<p>
The <code>|</code> character can also be used as an alias for
<code>FILTER</code>.
</p>
<pre>[% INCLUDE mytext | html %]</pre>
<p>
Multiple filters can be chained together and will be called in sequence.
</p>
<pre>[% INCLUDE mytext FILTER html FILTER html_para %]</pre>
<p>
or
</p>
<pre>[% INCLUDE mytext | html | html_para %]</pre>
<p>
Filters come in two flavours, known as 'static' or 'dynamic'. A static
filter is a simple subroutine which accepts a text string as the only
argument and returns the modified text. The <code>html</code> filter is
an example of a static filter, implemented as:
</p>
<pre>sub html_filter {
my $text = shift;
for ($text) {
s/&/&amp;/g;
s/</&lt;/g;
s/>/&gt;/g;
}
return $text;
}</pre>
<p>
Dynamic filters can accept arguments which are specified when the filter
is called from a template. The <code>repeat</code> filter is such an
example, accepting a numerical argument which specifies the number of
times that the input text should be repeated.
</p>
<pre>[% FILTER repeat(3) %]blah [% END %]</pre>
<p>
output:
</p>
<pre>blah blah blah</pre>
<p>
These are implemented as filter 'factories'. The factory subroutine is
passed a reference to the current <a href="../modules/Template/Context.html">Template::Context</a> object along
with any additional arguments specified. It should then return a
subroutine reference (e.g. a closure) which implements the filter. The
<code>repeat</code> filter factory is implemented like this:
</p>
<pre>sub repeat_filter_factory {
my ($context, $iter) = @_;
$iter = 1 unless defined $iter;
return sub {
my $text = shift;
$text = '' unless defined $text;
return join('\n', $text) x $iter;
}
}</pre>
<p>
The <code>FILTERS</code> option, described in <a href="../manual/Config.html">Template::Manual::Config</a>,
allows custom filters to be defined when a Template object is
instantiated. The <a
href="#method_define_filter">Template::Context#define_filter()</a> method
allows further filters to be defined at any time.
</p>
<p>
When using a filter, it is possible to assign an alias to it for further
use. This is most useful for dynamic filters that you want to re-use with
the same configuration.
</p>
<pre>[% FILTER echo = repeat(2) %]
Is there anybody out there?
[% END %]
[% FILTER echo %]
Mother, should I build a wall?
[% END %]</pre>
<p>
Output:
</p>
<pre>Is there anybody out there?
Is there anybody out there?</pre>
<pre>Mother, should I build a wall?
Mother, should I build a wall?</pre>
<p>
The <code>FILTER</code> directive automatically quotes the name of the
filter. As with <code>INCLUDE</code> et al, you can use a variable to
provide the name of the filter, prefixed by <code>$</code>.
</p>
<pre>[% myfilter = 'html' %]
[% FILTER $myfilter %] # same as [% FILTER html %]
...
[% END %]</pre>
<p>
A template variable can also be used to define a static filter
subroutine. However, the Template Toolkit will automatically call any
subroutine bound to a variable and use the value returned. Thus, the
above example could be implemented as:
</p>
<pre>my $vars = {
myfilter => sub { return 'html' },
};</pre>
<p>
template:
</p>
<pre>[% FILTER $myfilter %] # same as [% FILTER html %]
...
[% END %]</pre>
<p>
To define a template variable that evaluates to a subroutine reference
that can be used by the <code>FILTER</code> directive, you should create
a subroutine that, when called automatically by the Template Toolkit,
returns another subroutine reference which can then be used to perform
the filter operation. Note that only static filters can be implemented in
this way.
</p>
<pre>my $vars = {
myfilter => sub { \&my_filter_sub },
};
sub my_filter_sub {
my $text = shift;
# do something
return $text;
}</pre>
<p>
template:
</p>
<pre>[% FILTER $myfilter %]
...
[% END %]</pre>
<p>
Alternately, you can bless a subroutine reference into a class (any class
will do) to fool the Template Toolkit into thinking it's an object rather
than a subroutine. This will then bypass the automatic
"call-a-subroutine-to-return-a-value" magic.
</p>
<pre>my $vars = {
myfilter => bless(\&my_filter_sub, 'anything_you_like'),
};</pre>
<p>
template:
</p>
<pre>[% FILTER $myfilter %]
...
[% END %]</pre>
<p>
Filters bound to template variables remain local to the variable context
in which they are defined. That is, if you define a filter in a
<code>PERL</code> block within a template that is loaded via
<code>INCLUDE</code>, then the filter definition will only exist until
the end of that template when the stash is delocalised, restoring the
previous variable state. If you want to define a filter which persists
for the lifetime of the processor, or define additional dynamic filter
factories, then you can call the <a
href="#method_define_filter">Template::Context#define_filter()</a> method
on the current <a href="../modules/Template/Context.html">Template::Context</a> object.
</p>
<p>
See <a href="../manual/Filters.html">Template::Manual::Filters</a> for a complete list of available
filters, their descriptions and examples of use.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_USE" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">USE</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>USE</code> directive can be used to load and initialise
"plugin" extension modules.
</p>
<pre>[% USE myplugin %]</pre>
<p>
A plugin is a regular Perl module that conforms to a particular
object-oriented interface, allowing it to be loaded into and used
automatically by the Template Toolkit. For details of this interface and
information on writing plugins, consult <a href="../modules/Template/Plugin.html">Template::Plugin</a>.
</p>
<p>
A number of standard plugins are included with the Template Toolkit (see
below and <a href="../manual/Plugins.html">Template::Manual::Plugins</a>). The names of these standard plugins
are case insensitive.
</p>
<pre>[% USE CGI %] # => Template::Plugin::CGI
[% USE Cgi %] # => Template::Plugin::CGI
[% USE cgi %] # => Template::Plugin::CGI</pre>
<p>
You can also define further plugins using the <code>PLUGINS</code>
option.
</p>
<pre>my $tt = Template->new({
PLUGINS => {
foo => 'My::Plugin::Foo',
bar => 'My::Plugin::Bar',
},
});</pre>
<p>
The recommended convention is to specify these plugin names in lower
case. The Template Toolkit first looks for an exact case-sensitive match
and then tries the lower case conversion of the name specified.
</p>
<pre>[% USE Foo %] # look for 'Foo' then 'foo'</pre>
<p>
If you define all your <code>PLUGINS</code> with lower case names then
they will be located regardless of how the user specifies the name in the
<code>USE</code> directive. If, on the other hand, you define your
<code>PLUGINS</code> with upper or mixed case names then the name
specified in the <code>USE</code> directive must match the case exactly.
</p>
<p>
If the plugin isn't defined in either the standard plugins
(<code>$Template::Plugins::STD_PLUGINS</code>) or via the
<code>PLUGINS</code> option, then the <code>PLUGIN_BASE</code> is
searched.
</p>
<p>
In this case the plugin name <i>is</i> case-sensitive. It is appended to
each of the <code>PLUGIN_BASE</code> module namespaces in turn (default:
<code>Template::Plugin</code>) to construct a full module name which it
attempts to locate and load. Any periods, '<code>.</code>', in the name
will be converted to '<code>::</code>'.
</p>
<pre>[% USE MyPlugin %] # => Template::Plugin::MyPlugin
[% USE Foo.Bar %] # => Template::Plugin::Foo::Bar</pre>
<p>
The <code>LOAD_PERL</code> option (disabled by default) provides a
further way by which external Perl modules may be loaded. If a regular
Perl module (i.e. not a <code>Template::Plugin::*</code> or other module
relative to some <code>PLUGIN_BASE</code>) supports an object-oriented
interface and a <code>new()</code> constructor then it can be loaded and
instantiated automatically. The following trivial example shows how the
IO::File module might be used.
</p>
<pre>[% USE file = IO.File('/tmp/mydata') %]
[% WHILE (line = file.getline) %]
<!-- [% line %] -->
[% END %]</pre>
<p>
Any additional parameters supplied in parenthesis after the plugin name
will be also be passed to the <code>new()</code> constructor. A reference
to the current <a href="../modules/Template/Context.html">Template::Context</a> object is passed as the first parameter.
</p>
<pre>[% USE MyPlugin('foo', 123) %]</pre>
<p>
equivalent to:
</p>
<pre>Template::Plugin::MyPlugin->new($context, 'foo', 123);</pre>
<p>
The only exception to this is when a module is loaded via the
<code>LOAD_PERL</code> option. In this case the <code>$context</code>
reference is <i>not</i> passed to the <code>new()</code> constructor.
This is based on the assumption that the module is a regular Perl module
rather than a Template Toolkit plugin so isn't expecting a context
reference and wouldn't know what to do with it anyway.
</p>
<p>
Named parameters may also be specified. These are collated into a hash
which is passed by reference as the last parameter to the constructor, as
per the general code calling interface.
</p>
<pre>[% USE url('/cgi-bin/foo', mode='submit', debug=1) %]</pre>
<p>
equivalent to:
</p>
<pre>Template::Plugin::URL->new(
$context,
'/cgi-bin/foo'
{ mode => 'submit', debug => 1 }
);</pre>
<p>
The plugin may represent any data type; a simple variable, hash, list or
code reference, but in the general case it will be an object reference.
Methods can be called on the object (or the relevant members of the
specific data type) in the usual way:
</p>
<pre>[% USE table(mydata, rows=3) %]
[% FOREACH row IN table.rows %]
<tr>
[% FOREACH item IN row %]
<td>[% item %]</td>
[% END %]
</tr>
[% END %]</pre>
<p>
An alternative name may be provided for the plugin by which it can be
referenced:
</p>
<pre>[% USE scores = table(myscores, cols=5) %]
[% FOREACH row IN scores.rows %]
...
[% END %]</pre>
<p>
You can use this approach to create multiple plugin objects with
different configurations. This example shows how the <a
href="#section_format">Template::Plugin::Format</a> plugin is used to
create sub-routines bound to variables for formatting text as per
<code>printf()</code>.
</p>
<pre>[% USE bold = format('<b>%s</b>') %]
[% USE ital = format('<i>%s</i>') %]
[% bold('This is bold') %]
[% ital('This is italic') %]</pre>
<p>
Output:
</p>
<pre><b>This is bold</b>
<i>This is italic</i></pre>
<p>
This next example shows how the <a
href="#section_URL">Template::Plugin::URL</a> plugin can be used to build
dynamic URLs from a base part and optional query parameters.
</p>
<pre>[% USE mycgi = URL('/cgi-bin/foo.pl', debug=1) %]
<a href="[% mycgi %]">...
<a href="[% mycgi(mode='submit') %]"...</pre>
<p>
Output:
</p>
<pre><a href="/cgi-bin/foo.pl?debug=1">...
<a href="/cgi-bin/foo.pl?mode=submit&debug=1">...</pre>
<p>
The <a href="http://search.cpan.org/search?query=CGI&mode=all">Template::Plugin::CGI</a> plugin is
an example of one which delegates to another Perl module. In this this
case, to Lincoln Stein's <code>CGI</code> module. All of the methods
provided by the <code>CGI</code> module are available via the plugin.
</p>
<pre>[% USE CGI;
CGI.start_form;
CGI.checkbox_group( name = 'colours',
values = [ 'red' 'green' 'blue' ] );
CGI.popup_menu( name = 'items',
values = [ 'foo' 'bar' 'baz' ] );
CGI.end_form
%]</pre>
<p>
See <a href="../manual/Plugins.html">Template::Manual::Plugins</a> for more information on the plugins
distributed with the toolkit or available from CPAN.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_MACRO" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">MACRO</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>MACRO</code> directive allows you to define a directive or
directive block which is then evaluated each time the macro is called.
</p>
<pre>[% MACRO header INCLUDE header %]</pre>
<p>
Calling the macro as:
</p>
<pre>[% header %]</pre>
<p>
is then equivalent to:
</p>
<pre>[% INCLUDE header %]</pre>
<p>
Macros can be passed named parameters when called. These values remain
local to the macro.
</p>
<pre>[% header(title='Hello World') %] </pre>
<p>
equivalent to:
</p>
<pre>[% INCLUDE header title='Hello World' %]</pre>
<p>
A <code>MACRO</code> definition may include parameter names. Values
passed to the macros are then mapped to these local variables. Other
named parameters may follow these.
</p>
<pre>[% MACRO header(title) INCLUDE header %]
[% header('Hello World') %]
[% header('Hello World', bgcol='#123456') %]</pre>
<p>
equivalent to:
</p>
<pre>[% INCLUDE header title='Hello World' %]
[% INCLUDE header title='Hello World' bgcol='#123456' %]</pre>
<p>
Here's another example, defining a macro for display numbers in
comma-delimited groups of 3, using the chunk and join virtual method.
</p>
<pre>[% MACRO number(n) GET n.chunk(-3).join(',') %]
[% number(1234567) %] # 1,234,567</pre>
<p>
A <code>MACRO</code> may precede any directive and must conform to the
structure of the directive.
</p>
<pre>[% MACRO header IF frames %]
[% INCLUDE frames/header %]
[% ELSE %]
[% INCLUDE header %]
[% END %]
[% header %]</pre>
<p>
A <code>MACRO</code> may also be defined as an anonymous
<code>BLOCK</code>. The block will be evaluated each time the macro is
called.
</p>
<pre>[% MACRO header BLOCK %]
...content...
[% END %]
[% header %]</pre>
<p>
If you've got the <code>EVAL_PERL</code> option set, then you can even
define a <code>MACRO</code> as a <code>PERL</code> block (see below):
</p>
<pre>[% MACRO triple(n) PERL %]
my $n = $stash->get('n');
print $n * 3;
[% END -%]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_PERL" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">PERL</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
(for the advanced reader)
</p>
<p>
The <code>PERL</code> directive is used to mark the start of a block
which contains Perl code for evaluation. The <code>EVAL_PERL</code>
option must be enabled for Perl code to be evaluated or a
<code>perl</code> exception will be thrown with the message
'<code>EVAL_PERL not set</code>'.
</p>
<p>
Perl code is evaluated in the <code>Template::Perl</code> package. The
<code>$context</code> package variable contains a reference to the
current <a href="../modules/Template/Context.html">Template::Context</a> object. This can be used to access the
functionality of the Template Toolkit to process other templates, load
plugins, filters, etc. See <a href="../modules/Template/Context.html">Template::Context</a> for further details.
</p>
<pre>[% PERL %]
print $context->include('myfile');
[% END %]</pre>
<p>
The <a href="#section_$stash">$stash</a> variable contains a reference to
the top-level stash object which manages template variables. Through
this, variable values can be retrieved and updated. See <a href="../modules/Template/Stash.html">Template::Stash</a> for further
details.
</p>
<pre>[% PERL %]
$stash->set(foo => 'bar');
print "foo value: ", $stash->get('foo');
[% END %]</pre>
<p>
Output:
</p>
<pre>foo value: bar</pre>
<p>
Output is generated from the <code>PERL</code> block by calling
<code>print()</code>. Note that the <code>Template::Perl::PERLOUT</code>
handle is selected (tied to an output buffer) instead of
<code>STDOUT</code>.
</p>
<pre>[% PERL %]
print "foo\n"; # OK
print PERLOUT "bar\n"; # OK, same as above
print Template::Perl::PERLOUT "baz\n"; # OK, same as above
print STDOUT "qux\n"; # WRONG!
[% END %]</pre>
<p>
The <code>PERL</code> block may contain other template directives. These
are processed before the Perl code is evaluated.
</p>
<pre>[% name = 'Fred Smith' %]
[% PERL %]
print "[% name %]\n";
[% END %]</pre>
<p>
Thus, the Perl code in the above example is evaluated as:
</p>
<pre>print "Fred Smith\n";</pre>
<p>
Exceptions may be thrown from within <code>PERL</code> blocks using
<code>die()</code>. They will be correctly caught by enclosing
<code>TRY</code> blocks.
</p>
<pre>[% TRY %]
[% PERL %]
die "nothing to live for\n";
[% END %]
[% CATCH %]
error: [% error.info %]
[% END %]</pre>
<p>
output: error: nothing to live for
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_RAWPERL" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">RAWPERL</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
(for the very advanced reader)
</p>
<p>
The Template Toolkit parser reads a source template and generates the
text of a Perl subroutine as output. It then uses <code>eval()</code> to
evaluate it into a subroutine reference. This subroutine is then called
to process the template, passing a reference to the current <a href="../modules/Template/Context.html">Template::Context</a> object through
which the functionality of the Template Toolkit can be accessed. The
subroutine reference can be cached, allowing the template to be processed
repeatedly without requiring any further parsing.
</p>
<p>
For example, a template such as:
</p>
<pre>[% PROCESS header %]
The [% animal %] sat on the [% location %]
[% PROCESS footer %]</pre>
<p>
is converted into the following Perl subroutine definition:
</p>
<pre>sub {
my $context = shift;
my $stash = $context->stash;
my $output = '';
my $error;
eval { BLOCK: {
$output .= $context->process('header');
$output .= "The ";
$output .= $stash->get('animal');
$output .= " sat on the ";
$output .= $stash->get('location');
$output .= $context->process('footer');
$output .= "\n";
} };
if ($@) {
$error = $context->catch($@, \$output);
die $error unless $error->type eq 'return';
}
return $output;
}</pre>
<p>
To examine the Perl code generated, such as in the above example, set the
<code>$Template::Parser::DEBUG</code> package variable to any true value.
You can also set the <code>$Template::Directive::PRETTY</code> variable
true to have the code formatted in a readable manner for human
consumption. The source code for each generated template subroutine will
be printed to <code>STDERR</code> on compilation (i.e. the first time a
template is used).
</p>
<pre>$Template::Parser::DEBUG = 1;
$Template::Directive::PRETTY = 1;
$template->process($file, $vars)
|| die $template->error(), "\n";</pre>
<p>
The <code>PERL</code> ... <code>END</code> construct allows Perl code to
be embedded into a template when the <code>EVAL_PERL</code> option is
set. It is evaluated at "runtime" using <code>eval()</code> each time the
template subroutine is called. This is inherently flexible, but not as
efficient as it could be, especially in a persistent server environment
where a template may be processed many times.
</p>
<p>
The <code>RAWPERL</code> directive allows you to write Perl code that is
integrated directly into the generated Perl subroutine text. It is
evaluated once at compile time and is stored in cached form as part of
the compiled template subroutine. This makes <code>RAWPERL</code> blocks
more efficient than <code>PERL</code> blocks.
</p>
<p>
The downside is that you must code much closer to the metal. For example,
in a <code>PERL</code> block you can call <a
href="#method_print">print()</a> to generate some output.
<code>RAWPERL</code> blocks don't afford such luxury. The code is
inserted directly into the generated subroutine text and should conform
to the convention of appending to the <code>$output</code> variable.
</p>
<pre>[% PROCESS header %]
[% RAWPERL %]
$output .= "Some output\n";
...
$output .= "Some more output\n";
[% END %]</pre>
<p>
The critical section of the generated subroutine for this example would
then look something like:
</p>
<pre>...
eval { BLOCK: {
$output .= $context->process('header');
$output .= "\n";
$output .= "Some output\n";
...
$output .= "Some more output\n";
$output .= "\n";
} };
...</pre>
<p>
As with <code>PERL</code> blocks, the <a
href="#section_$context">Template::Context</a> and <a
href="#section_$stash">Template::Stash</a> references are pre-defined and
available for use within <code>RAWPERL</code> code.
</p>
</div>
</div>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Exception_Handling_and_Flow_Control" onclick="switch_section(this)" title="Click title to show/hide section content.">Exception Handling and Flow Control</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<div class="subsection">
<div class="head">
<h2 id="section_TRY_THROW_CATCH_FINAL" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">TRY / THROW / CATCH / FINAL</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
(more advanced material)
</p>
<p>
The Template Toolkit supports fully functional, nested exception
handling. The <code>TRY</code> directive introduces an exception handling
scope which continues until the matching <code>END</code> directive. Any
errors that occur within that block will be caught and can be handled by
one of the <code>CATCH</code> blocks defined.
</p>
<pre>[% TRY %]
...blah...blah...
[% CALL somecode %]
...etc...
[% INCLUDE someblock %]
...and so on...
[% CATCH %]
An error occurred!
[% END %]</pre>
<p>
Errors are raised as exceptions (objects of the <a href="../modules/Template/Exception.html">Template::Exception</a> class)
which contain two fields: <code>type</code> and <code>info</code>. The
exception <code>type</code> is used to indicate the kind of error that
occurred. It is a simple text string which can contain letters, numbers,
'<code>_</code>' or '<code>.</code>'. The <code>info</code> field
contains an error message indicating what actually went wrong. Within a
catch block, the exception object is aliased to the <code>error</code>
variable. You can access the <code>type</code> and <code>info</code>
fields directly.
</p>
<pre>[% mydsn = 'dbi:MySQL:foobar' %]
...
[% TRY %]
[% USE DBI(mydsn) %]
[% CATCH %]
ERROR! Type: [% error.type %]
Info: [% error.info %]
[% END %]</pre>
<p>
output (assuming a non-existant database called '<code>foobar</code>'):
</p>
<pre>ERROR! Type: DBI
Info: Unknown database "foobar"</pre>
<p>
The <code>error</code> variable can also be specified by itself and will
return a string of the form "<code>$type error - $info</code>".
</p>
<pre>...
[% CATCH %]
ERROR: [% error %]
[% END %]</pre>
<p>
Output:
</p>
<pre>ERROR: DBI error - Unknown database "foobar"</pre>
<p>
Each <code>CATCH</code> block may be specified with a particular
exception type denoting the kind of error that it should catch. Multiple
<code>CATCH</code> blocks can be provided to handle different types of
exception that may be thrown in the <code>TRY</code> block. A
<code>CATCH</code> block specified without any type, as in the previous
example, is a default handler which will catch any otherwise uncaught
exceptions. This can also be specified as <code>[% CATCH DEFAULT
%]</code>.
</p>
<pre>[% TRY %]
[% INCLUDE myfile %]
[% USE DBI(mydsn) %]
[% CALL somecode %]
[% CATCH file %]
File Error! [% error.info %]
[% CATCH DBI %]
[% INCLUDE database/error.html %]
[% CATCH %]
[% error %]
[% END %]</pre>
<p>
Remember that you can specify multiple directives within a single tag,
each delimited by '<code>;</code>'. So the above example can be written
more concisely as:
</p>
<pre>[% TRY;
INCLUDE myfile;
USE DBI(mydsn);
CALL somecode;
CATCH file;
"File Error! $error.info";
CATCH DBI;
INCLUDE database/error.html;
CATCH;
error;
END
%]</pre>
<p>
The <code>DBI</code> plugin throws exceptions of the <code>DBI</code>
type (in case that wasn't already obvious). The other specific exception
caught here is of the <code>file</code> type.
</p>
<p>
A <code>file</code> exception is automatically thrown by the Template
Toolkit when it can't find a file, or fails to load, parse or process a
file that has been requested by an <code>INCLUDE</code>,
<code>PROCESS</code>, <code>INSERT</code> or <code>WRAPPER</code>
directive. If <code>myfile</code> can't be found in the example above,
the <code>[% INCLUDE myfile %]</code> directive will raise a
<code>file</code> exception which is then caught by the <code>[% CATCH
file %]</code> block. The output generated would be:
</p>
<pre>File Error! myfile: not found</pre>
<p>
Note that the <code>DEFAULT</code> option (disabled by default) allows
you to specify a default file to be used any time a template file can't
be found. This will prevent file exceptions from ever being raised when a
non-existant file is requested (unless, of course, the
<code>DEFAULT</code> file your specify doesn't exist). Errors encountered
once the file has been found (i.e. read error, parse error) will be
raised as file exceptions as per usual.
</p>
<p>
Uncaught exceptions (i.e. if the <code>TRY</code> block doesn't have a
type specific or default <code>CATCH</code> handler) may be caught by
enclosing <code>TRY</code> blocks which can be nested indefinitely across
multiple templates. If the error isn't caught at any level then
processing will stop and the Template <a
href="#method_process">Template#process()</a> method will return a false
value to the caller. The relevant <a href="../modules/Template/Exception.html">Template::Exception</a> object can
be retrieved by calling the <a href="#method_error">Template#error()</a>
method.
</p>
<pre>[% TRY %]
...
[% TRY %]
[% INCLUDE $user.header %]
[% CATCH file %]
[% INCLUDE header %]
[% END %]
...
[% CATCH DBI %]
[% INCLUDE database/error.html %]
[% END %]</pre>
<p>
In this example, the inner <code>TRY</code> block is used to ensure that
the first <code>INCLUDE</code> directive works as expected. We're using a
variable to provide the name of the template we want to include,
<code>user.header</code>, and it's possible this contains the name of a
non-existant template, or perhaps one containing invalid template
directives. If the <code>INCLUDE</code> fails with a <code>file</code>
error then we <code>CATCH</code> it in the inner block and
<code>INCLUDE</code> the default <code>header</code> file instead. Any
<code>DBI</code> errors that occur within the scope of the outer
<code>TRY</code> block will be caught in the relevant <code>CATCH</code>
block, causing the <code>database/error.html</code> template to be
processed. Note that included templates inherit all currently defined
template variable so these error files can quite happily access the
<error> variable to retrieve information about the currently caught
exception. For example, the <code>database/error.html</code> template
might look like this:
</p>
<pre><h2>Database Error</h2>
A database error has occurred: [% error.info %]</pre>
<p>
You can also specify a <code>FINAL</code> block. This is always processed
regardless of the outcome of the <code>TRY</code> and/or
<code>CATCH</code> blocks. If an exception is uncaught then the
<code>FINAL</code> block is processed before jumping to the enclosing
block or returning to the caller.
</p>
<pre>[% TRY %]
...
[% CATCH this %]
...
[% CATCH that %]
...
[% FINAL %]
All done!
[% END %]</pre>
<p>
The output from the <code>TRY</code> block is left intact up to the point
where an exception occurs. For example, this template:
</p>
<pre>[% TRY %]
This gets printed
[% THROW food 'carrots' %]
This doesn't
[% CATCH food %]
culinary delights: [% error.info %]
[% END %] </pre>
<p>
generates the following output:
</p>
<pre>This gets printed
culinary delights: carrots</pre>
<p>
The <code>CLEAR</code> directive can be used in a <code>CATCH</code> or
<code>FINAL</code> block to clear any output created in the
<code>TRY</code> block.
</p>
<pre>[% TRY %]
This gets printed
[% THROW food 'carrots' %]
This doesn't
[% CATCH food %]
[% CLEAR %]
culinary delights: [% error.info %]
[% END %] </pre>
<p>
Output:
</p>
<pre>culinary delights: carrots</pre>
<p>
Exception types are hierarchical, with each level being separated by the
familiar dot operator. A <code>DBI.connect</code> exception is a more
specific kind of <code>DBI</code> error. Similarly, an
<code>example.error.barf</code> is a more specific kind of
<code>example.error</code> type which itself is also a
<code>example</code> error.
</p>
<p>
A <code>CATCH</code> handler that specifies a general exception type
(such as <code>DBI</code> or <code>example.error</code>) will also catch
more specific types that have the same prefix as long as a more specific
handler isn't defined. Note that the order in which <code>CATCH</code>
handlers are defined is irrelevant; a more specific handler will always
catch an exception in preference to a more generic or default one.
</p>
<pre>[% TRY %]
...
[% CATCH DBI ;
INCLUDE database/error.html ;
CATCH DBI.connect ;
INCLUDE database/connect.html ;
CATCH ;
INCLUDE error.html ;
END
%]</pre>
<p>
In this example, a <code>DBI.connect</code> error has it's own handler, a
more general <code>DBI</code> block is used for all other
<code>DBI</code> or <code>DBI.*</code> errors and a default handler
catches everything else.
</p>
<p>
Exceptions can be raised in a template using the <code>THROW</code>
directive. The first parameter is the exception type which doesn't need
to be quoted (but can be, it's the same as <code>INCLUDE</code>) followed
by the relevant error message which can be any regular value such as a
quoted string, variable, etc.
</p>
<pre>[% THROW food "Missing ingredients: $recipe.error" %]
[% THROW user.login 'no user id: please login' %]
[% THROW $myerror.type "My Error: $myerror.info" %]</pre>
<p>
It's also possible to specify additional positional or named parameters
to the <code>THROW</code> directive if you want to pass more than just a
simple message back as the error info field.
</p>
<pre>[% THROW food 'eggs' 'flour' msg='Missing Ingredients' %]</pre>
<p>
In this case, the error <code>info</code> field will be a hash array
containing the named arguments and an <code>args</code> item which
contains a list of the positional arguments.
</p>
<pre>type => 'food',
info => {
msg => 'Missing Ingredients',
args => ['eggs', 'flour'],
}</pre>
<p>
In addition to specifying individual positional arguments as <code>[%
error.info.args.n %]</code>, the <code>info</code> hash contains keys
directly pointing to the positional arguments, as a convenient shortcut.
</p>
<pre>[% error.info.0 %] # same as [% error.info.args.0 %]</pre>
<p>
Exceptions can also be thrown from Perl code which you've bound to
template variables, or defined as a plugin or other extension. To raise
an exception, call <code>die()</code> passing a reference to a <a
href="../modules/Template/Exception.html">Template::Exception</a>
object as the argument. This will then be caught by any enclosing
<code>TRY</code> blocks from where the code was called.
</p>
<pre>use Template::Exception;
...
my $vars = {
foo => sub {
# ... do something ...
die Template::Exception->new('myerr.naughty',
'Bad, bad error');
},
};</pre>
<p>
Template:
</p>
<pre>[% TRY %]
[% foo %]
[% CATCH myerr ;
"Error: $error" ;
END
%]</pre>
<p>
Output:
</p>
<pre>Error: myerr.naughty error - Bad, bad error</pre>
<p>
The <code>info</code> field can also be a reference to another object or
data structure, if required.
</p>
<pre>die Template::Exception->new('myerror', {
module => 'foo.pl',
errors => [ 'bad permissions', 'naughty boy' ],
});</pre>
<p>
Later, in a template:
</p>
<pre>[% TRY %]
...
[% CATCH myerror %]
[% error.info.errors.size or 'no';
error.info.errors.size == 1 ? ' error' : ' errors' %]
in [% error.info.module %]:
[% error.info.errors.join(', ') %].
[% END %]</pre>
<p>
Generating the output:
</p>
<pre>2 errors in foo.pl:
bad permissions, naughty boy.</pre>
<p>
You can also call <code>die()</code> with a single string, as is common
in much existing Perl code. This will automatically be converted to an
exception of the '<code>undef</code>' type (that's the literal string
'<code>undef</code>', not the undefined value). If the string isn't
terminated with a newline then Perl will append the familiar <code>" at
$file line $line"</code> message.
</p>
<pre>sub foo {
# ... do something ...
die "I'm sorry, Dave, I can't do that\n";
}</pre>
<p>
If you're writing a plugin, or some extension code that has the current
<a href="../modules/Template/Context.html">Template::Context</a> in
scope (you can safely skip this section if this means nothing to you)
then you can also raise an exception by calling the context <a
href="#method_throw">Template::Context#throw()</a> method. You can pass
it an <a href="../modules/Template/Exception.html">Template::Exception</a> object reference, a pair of <code>($type,
$info)</code> parameters or just an <code>$info</code> string to create
an exception of '<code>undef</code>' type.
</p>
<pre>$context->throw($e); # exception object
$context->throw('Denied'); # 'undef' type
$context->throw('user.passwd', 'Bad Password');</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_NEXT" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">NEXT</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>NEXT</code> directive can be used to start the next iteration
of a <code>FOREACH</code> or <code>WHILE</code> loop.
</p>
<pre>[% FOREACH user IN users %]
[% NEXT IF user.isguest %]
Name: [% user.name %] Email: [% user.email %]
[% END %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_LAST" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">LAST</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>LAST</code> directive can be used to prematurely exit a
<code>FOREACH</code> or <code>WHILE</code> loop.
</p>
<pre>[% FOREACH user IN users %]
Name: [% user.name %] Email: [% user.email %]
[% LAST IF some.condition %]
[% END %]</pre>
<p>
<code>BREAK</code> can also be used as an alias for <code>LAST</code>.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_RETURN" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">RETURN</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>RETURN</code> directive can be used to stop processing the
current template and return to the template from which it was called,
resuming processing at the point immediately after the
<code>INCLUDE</code>, <code>PROCESS</code> or <code>WRAPPER</code>
directive. If there is no enclosing template then the Template <a
href="#method_process">Template#process()</a> method will return to the
calling code with a true value.
</p>
<pre>Before
[% INCLUDE half_wit %]
After
[% BLOCK half_wit %]
This is just half...
[% RETURN %]
...a complete block
[% END %]</pre>
<p>
Output:
</p>
<pre>Before
This is just half...
After</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_STOP" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">STOP</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>STOP</code> directive can be used to indicate that the
processor should stop gracefully without processing any more of the
template document. This is a planned stop and the Template <a
href="#method_process">Template#process()</a> method will return a
<b>true</b> value to the caller. This indicates that the template was
processed successfully according to the directives within it.
</p>
<pre>[% IF something.terrible.happened %]
[% INCLUDE fatal/error.html %]
[% STOP %]
[% END %]
[% TRY %]
[% USE DBI(mydsn) %]
...
[% CATCH DBI.connect %]
<h1>Cannot connect to the database: [% error.info %]</h1>
<p>
We apologise for the inconvenience.
</p>
[% INCLUDE footer %]
[% STOP %]
[% END %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_CLEAR" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">CLEAR</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>CLEAR</code> directive can be used to clear the output buffer
for the current enclosing block. It is most commonly used to clear the
output generated from a <code>TRY</code> block up to the point where the
error occurred.
</p>
<pre>[% TRY %]
blah blah blah # this is normally left intact
[% THROW some 'error' %] # up to the point of error
...
[% CATCH %]
[% CLEAR %] # clear the TRY output
[% error %] # print error string
[% END %]</pre>
</div>
</div>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Miscellaneous" onclick="switch_section(this)" title="Click title to show/hide section content.">Miscellaneous</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<div class="subsection">
<div class="head">
<h2 id="section_META" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">META</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>META</code> directive allows simple metadata items to be
defined within a template. These are evaluated when the template is
parsed and as such may only contain simple values (e.g. it's not possible
to interpolate other variables values into <code>META</code> variables).
</p>
<pre>[% META
title = 'The Cat in the Hat'
author = 'Dr. Seuss'
version = 1.23
%]</pre>
<p>
The <code>template</code> variable contains a reference to the main
template being processed. These metadata items may be retrieved as
attributes of the template.
</p>
<pre><h1>[% template.title %]</h1>
<h2>[% template.author %]</h2></pre>
<p>
The <code>name</code> and <code>modtime</code> metadata items are
automatically defined for each template to contain its name and
modification time in seconds since the epoch.
</p>
<pre>[% USE date %] # use Date plugin to format time
...
[% template.name %] last modified
at [% date.format(template.modtime) %]</pre>
<p>
The <code>PRE_PROCESS</code> and <code>POST_PROCESS</code> options allow
common headers and footers to be added to all templates. The
<code>template</code> reference is correctly defined when these templates
are processed, allowing headers and footers to reference metadata items
from the main template.
</p>
<pre>$template = Template->new({
PRE_PROCESS => 'header',
POST_PROCESS => 'footer',
});
$template->process('cat_in_hat');</pre>
<p>
header:
</p>
<pre><html>
<head>
<title>[% template.title %]</title>
</head>
<body></pre>
<p>
cat_in_hat:
</p>
<pre>[% META
title = 'The Cat in the Hat'
author = 'Dr. Seuss'
version = 1.23
year = 2000
%]
The cat in the hat sat on the mat.</pre>
<p>
footer:
</p>
<pre> <hr>
&copy; [% template.year %] [% template.author %]
</body>
</html></pre>
<p>
The output generated from the above example is:
</p>
<pre><html>
<head>
<title>The Cat in the Hat</title>
</head>
<body>
The cat in the hat sat on the mat.
<hr>
&copy; 2000 Dr. Seuss
</body>
</html></pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_TAGS" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">TAGS</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>TAGS</code> directive can be used to set the
<code>START_TAG</code> and <code>END_TAG</code> values on a per-template
file basis.
</p>
<pre>[% TAGS <+ +> %]
<+ INCLUDE header +></pre>
<p>
The TAGS directive may also be used to set a named <code>TAG_STYLE</code>
</p>
<pre>[% TAGS html %]
<!-- INCLUDE header --></pre>
<p>
See the <a href="#section_TAGS">Template::Manual::Config#TAGS</a> and <a
href="#section_TAG_STYLE">Template::Manual::Config#TAG_STYLE</a>
configuration options for further details.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_DEBUG" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">DEBUG</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>DEBUG</code> directive can be used to enable or disable
directive debug messages within a template. The <code>DEBUG</code>
configuration option must be set to include <code>DEBUG_DIRS</code> for
the <code>DEBUG</code> directives to have any effect. If
<code>DEBUG_DIRS</code> is not set then the parser will automatically
ignore and remove any <code>DEBUG</code> directives.
</p>
<p>
The <code>DEBUG</code> directive can be used with an <code>on</code> or
<code>off</code> parameter to enable or disable directive debugging
messages from that point forward. When enabled, the output of each
directive in the generated output will be prefixed by a comment indicate
the file, line and original directive text.
</p>
<pre>[% DEBUG on %]
directive debugging is on (assuming DEBUG option is set true)
[% DEBUG off %]
directive debugging is off</pre>
<p>
The <code>format</code> parameter can be used to change the format of the
debugging message.
</p>
<pre>[% DEBUG format '<!-- $file line $line : [% $text %] -->' %]</pre>
</div>
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