#============================================================= -*-perl-*-
#
# Template::Manual::Directives
#
# DESCRIPTION
#   This section provides a reference of all Template Toolkit
#   directives, complete with examples of use.
#
# AUTHOR
#   Andy Wardley  <abw@kfs.org>
#
# COPYRIGHT
#   Copyright (C) 1996-2001 Andy Wardley.  All Rights Reserved.
#   Copyright (C) 1998-2001 Canon Research Centre Europe Ltd.
#
#   This module is free software; you can redistribute it and/or
#   modify it under the same terms as Perl itself.
#
# REVISION
#   
#
#========================================================================


#------------------------------------------------------------------------
# IMPORTANT NOTE
#   This documentation is generated automatically from source
#   templates.  Any changes you make here may be lost.
# 
#   The 'docsrc' documentation source bundle is available for download
#   from http://www.template-toolkit.org/docs.html and contains all
#   the source templates, XML files, scripts, etc., from which the
#   documentation for the Template Toolkit is built.
#------------------------------------------------------------------------

=head1 NAME

Template::Manual::Directives - Template directives

=head1 DESCRIPTION

This section provides a reference of all Template Toolkit directives,
complete with examples of use.

=head2 Accessing and Updating Template Variables

=over 4


=item GET

The GET directive retrieves and outputs the value of the named variable.

    [% GET foo %]

The GET keyword is optional.  A variable can be specified in a directive
tag by itself.

    [% foo %]

The variable may take any of the forms described above:

    [% foo %]
    [% bar.baz %]
    [% biz.baz(10) %]
    ...etc...

You can also specify expressions using the logical (and, or, not, ?:) and
mathematic operators (+ - * / % mod div).

    [% template.title or default.title %]

    [% score * 100 %]

    [% order.nitems ? checkout(order.total) : 'no items' %]

The 'div' operator returns the integer result of division.  Both '%' and 
'mod' return the modulus (i.e. remainder) of division.  'mod' is provided
as an alias for '%' for backwards compatibility with version 1.

    [% 15 / 6 %]	    # 2.5
    [% 15 div 6 %]	    # 2
    [% 15 mod 6 %]	    # 3



=item CALL

The CALL directive is similar to GET 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.

    [% CALL dbi.disconnect %]

    [% CALL inc_page_counter(page_count) %]




=item SET

The SET directive allows you to assign new values to existing variables
or create new temporary variables.

    [% SET title = 'Hello World' %]

The SET keyword is also optional.
   
    [% title = 'Hello World' %]

Variables may be assigned the values of other variables, unquoted
numbers (digits), 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 '$', using curly braces to explicitly scope
the variable name where necessary.

    [% foo  = 'Foo'  %]               # literal value 'Foo'
    [% bar  =  foo   %]               # value of variable 'foo'
    [% cost = '$100' %]               # literal value '$100'
    [% item = "$bar: ${cost}.00" %]   # value "Foo: $100.00"

Multiple variables may be assigned in the same directive and are 
evaluated in the order specified.  Thus, the above could have been 
written:

    [% foo  = 'Foo'
       bar  = foo
       cost = '$100'
       item = "$bar: ${cost}.00"
    %]

Simple expressions can also be used, as per GET.

    [% ten    = 10 
       twenty = 20
       thirty = twenty + ten
       forty  = 2 * twenty 
       fifty  = 100 div 2
       six    = twenty mod 7
    %]





=item DEFAULT

The DEFAULT directive is similar to SET but only updates variables 
that are currently undefined or have no "true" value (in the Perl
sense).

    [% DEFAULT
       name = 'John Doe'
       id   = 'jdoe'
    %]

This can be particularly useful in common template components to
ensure that some sensible default are provided for otherwise 
undefined variables.

    [% DEFAULT 
       title = 'Hello World'
       bgcol = '#ffffff'
    %]
    <html>
    <head>
    <title>[% title %]</title>
    </head>

    <body bgcolor="[% bgcol %]">


=back

=head2 Processing Other Template Files and Blocks

=over 4


=item INSERT

The INSERT directive is used to insert the contents of an external file
at the current position.

    [% INSERT myfile %]

No attempt to parse or process the file is made.  The contents,
possibly including any embedded template directives, are inserted
intact.

The filename specified should be relative to one of the INCLUDE_PATH
directories.  Absolute (i.e. starting with C</>) and relative
(i.e. starting with C<.>) filenames may be used if the ABSOLUTE and
RELATIVE options are set, respectively.  Both these options are
disabled by default.

    my $template = Template->new({
	INCLUDE_PATH => '/here:/there',
    });

    $template->process('myfile');

'myfile':

    [% INSERT foo %]		# looks for /here/foo then /there/foo
    [% INSERT /etc/passwd %]	# file error: ABSOLUTE not set
    [% INSERT ../secret %]	# file error: RELATIVE not set

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.

    [% INSERT misc/legalese.txt            %]
    [% INSERT 'dos98/Program Files/stupid' %]

To evaluate a variable to specify a filename, you should explicitly
prefix it with a '$' or use double-quoted string interpolation.

    [% language = 'en'
       legalese = 'misc/legalese.txt' 
    %]

    [% INSERT $legalese %]		# 'misc/legalese.txt'
    [% INSERT "$language/$legalese" %]  # 'en/misc/legalese.txt'

Multiple files can be specified using '+' as a delimiter.  All files
should be unquoted names or quoted strings.  Any variables should be
interpolated into double-quoted strings.

    [% INSERT legalese.txt + warning.txt %]
    [% INSERT  "$legalese" + warning.txt %]  # requires quoting

















=item INCLUDE

The INCLUDE directive is used to process and include the output of
another template file or block.

    [% INCLUDE header %]

If a BLOCK 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.

    [% INCLUDE table %]		    # uses BLOCK defined below

    [% BLOCK table %]
       <table>
       ...
       </table>
    [% END %]

If a BLOCK definition is not currently visible then the template name
should be a file relative to one of the INCLUDE_PATH directories, or
an absolute or relative file name if the ABSOLUTE/RELATIVE options are
appropriately enabled.  The INCLUDE directive automatically quotes the
filename specified, as per INSERT described above.  When a variable
contains the name of the template for the INCLUDE directive, it should
be explicitly prefixed by '$' or double-quoted

    [% myheader = 'my/misc/header' %]
    [% INCLUDE   myheader  %]            # 'myheader'
    [% INCLUDE  $myheader  %]		 # 'my/misc/header'
    [% INCLUDE "$myheader" %]		 # 'my/misc/header'

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.  

    [% title = 'Hello World' %]
    [% INCLUDE header %]
    <body>
    ...

'header':

    <html>
    <title>[% title %]</title>

output:

    <html>
    <title>Hello World</title>
    <body>
    ...

Local variable definitions may be specified after the template name,
temporarily masking any existing variables.  Insignificant whitespace
is ignore 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.

    [% INCLUDE table %]

    [% INCLUDE table title="Active Projects" %]

    [% INCLUDE table 
	 title   = "Active Projects" 
         bgcolor = "#80ff00"	# chartreuse
	 border  = 2
    %]

The INCLUDE 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.

    [% foo = 10 %]

    foo is originally [% foo %]
    [% INCLUDE bar %]
    foo is still [% foo %]

    [% BLOCK bar %]
       foo was [% foo %]
       [% foo = 20 %]
       foo is now [% foo %]
    [% END %]

output:
    foo is originally 10
       foo was 10
       foo is now 20
    foo is still 10

Technical Note: the localisation of the stash (that is, the process by
which variables are copied before an INCLUDE 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 'foo'
variable referencing a hash will be copied to create a new 'foo'
variable but which points to the same hash array.  Thus, if you update
compound variables (e.g. foo.bar) 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 PROCESS directive which is
faster by virtue of not performing any localisation.

From version 2.04 onwards, you can specify dotted variables as "local"
variables to an INCLUDE 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.

    [% foo = {
           bar = 'Baz'
       }
    %]
  
    [% INCLUDE somefile foo.bar='Boz' %]

    [% foo.bar %]	    # Boz

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 INCLUDE and other similar directives.

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
'$variables') joined together by '+'.  The INCLUDE directive
will then process them in order.

    [% INCLUDE html/header + "site/$header" + site/menu
         title = "My Groovy Web Site"
    %]

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 INCLUDE
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.



=item PROCESS

The PROCESS directive is similar to INCLUDE 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.

    [% foo = 10 %]

    foo is [% foo %]
    [% PROCESS bar %]
    foo is [% foo %]

    [% BLOCK bar %]
       [% foo = 20 %]
       changed foo to [% foo %]
    [% END %]

output:

    foo is 10
       changed foo to 20
    foo is 20

Parameters may be specified in the PROCESS directive, but these too will 
become visible changes to current variable values.

    [% foo = 10 %]
    foo is [% foo %]
    [% PROCESS bar
       foo = 20 
    %]
    foo is [% foo %]

    [% BLOCK bar %]
       this is bar, foo is [% foo %]
    [% END %]

output:

    foo is 10
       this is bar, foo is 20
    foo is 20

The PROCESS directive is slightly faster than INCLUDE because it
avoids the need to localise (i.e. copy) the variable stash before
processing the template.  As with INSERT and INCLUDE, the first
parameter does not need to be quoted as long as it contains only
alphanumeric characters, underscores, periods or forward slashes.
A '$' prefix can be used to explicitly indicate a variable which 
should be interpolated to provide the template name:

    [% myheader = 'my/misc/header' %]
    [% PROCESS  myheader %]              # 'myheader'
    [% PROCESS $myheader %]		 # 'my/misc/header'

As with INCLUDE, multiple templates can be specified, delimited by
'+', and are processed in order.

    [% PROCESS html/header + my/header %]





=item WRAPPER

It's not unusual to find yourself adding common headers and footers to 
pages or sub-sections within a page.  Something like this:

    [% 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 %]

The individual template components being included might look like these:

section/header:

    <p>
    <h2>[% title %]</h2>

section/footer:

    </p>

The WRAPPER directive provides a way of simplifying this a little.  It
encloses a block up to a matching END directive, which is first
processed to generate some output.  This is then passed to the named
template file or BLOCK as the 'content' variable.

    [% 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 %]

The single 'section' template can then be defined as:

    <p>
    <h2>[% title %]</h2>
    [% content %]
    </p>

Like other block directives, it can be used in side-effect notation:

    [% INSERT legalese.txt WRAPPER big_bold_table %]

It's also possible to specify multiple templates to a WRAPPER directive.
The specification order indicates outermost to innermost wrapper templates.
For example, given the following template block definitions:

    [% BLOCK bold   %]<b>[% content %]</b>[% END %]
    [% BLOCK italic %]<i>[% content %]</i>[% END %]

the directive 

    [% WRAPPER bold+italic %]Hello World[% END %]

would generate the following output:

    <b><i>Hello World</i></b>



 














=item BLOCK

The BLOCK ... END construct can be used to define template component
blocks which can be processed with the INCLUDE, PROCESS and WRAPPER
directives.

    [% 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>

A BLOCK 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.

    [% PROCESS tmpblk %]

    [% BLOCK tmpblk %] This is OK [% END %]

You can use an anonymous BLOCK to capture the output of a template
fragment.  

    [% 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 %]

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 'julius'.

Anonymous BLOCKs can also be used to define block macros.  The
enclosing block is processed each time the macro is called.

    [% 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



=back

=head2 Conditional Processing

=over 4


=item IF / UNLESS / ELSIF / ELSE

The IF and UNLESS directives can be used to process or ignore a
block based on some run-time condition.  

    [% IF frames %]
       [% INCLUDE frameset %]
    [% END %]

    [% UNLESS text_mode %]
       [% INCLUDE biglogo %]
    [% END %]

Multiple conditions may be joined with ELSIF and/or ELSE blocks.

    [% 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 %]

The following conditional and boolean operators may be used:

    == != < <= > >= && || ! and or not

Note that C<and>, C<or> and C<not> are also provided as aliases for
C<&&>, C<||> and C<!>, respectively.

Conditions may be arbitrarily complex and are evaluated with the same
precedence as in Perl.  Parenthesis may be used to explicitly
determine evaluation order.

    # ridiculously contrived complex example
    [% IF (name == 'admin' || uid <= 0) && mode == 'debug' %]
       I'm confused.
    [% ELSIF more > less %]
       That's more or less correct.
    [% END %]






=item SWITCH / CASE

The SWITCH / CASE construct can be used to perform a multi-way
conditional test.  The SWITCH directive expects an expression which is
first evaluated and then compared against each CASE statement in turn.
Each CASE directive should contain a single value or a list of values
which should match.  CASE may also be left blank or written as [% CASE
DEFAULT %] to specify a default match.  Only one CASE matches, there
is no drop-through between CASE statements.

    [% SWITCH myvar %]
    [% CASE value1 %]
       ...
    [% CASE [ value2 value3 ] %]   # multiple values
       ...
    [% CASE myhash.keys %]         # ditto
       ...
    [% CASE %]                     # default
       ...
    [% END %]
  



=back

=head2 Loop Processing

=over 4


=item FOREACH

The FOREACH directive will iterate through the items in a list, processing
the enclosed block for each one.

    my $vars = {
	foo   => 'Foo',
  	items => [ 'one', 'two', 'three' ],
    };
  
template:

    Things:
    [% FOREACH thing = [ foo 'Bar' "$foo Baz" ] %]
       * [% thing %]
    [% END %]
  
    Items:
    [% FOREACH i = items %]
       * [% i %]
    [% END %]
  
    Stuff:
    [% stuff = [ foo "$foo Bar" ] %]
    [% FOREACH s = stuff %]
       * [% s %]
    [% END %]

output:

    Things:
      * Foo
      * Bar
      * Foo Baz
  
    Items:
      * one
      * two
      * three
  
    Stuff:
      * Foo
      * Foo Bar

When the FOREACH directive is used without specifying a target variable, 
any iterated values which are hash references will be automatically 
imported.

    [% userlist = [
	  { id => 'tom',   name => 'Thomas'  },
	  { id => 'dick',  name => 'Richard'  },
	  { id => 'larry', name => 'Lawrence' },
       ]
    %]

    [% FOREACH user = userlist %]
       [% user.id %] [% user.name %]
    [% END %]

short form:

    [% FOREACH userlist %]
       [% id %] [% name %]
    [% END %]

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 FOREACH loop will be lost at the end of the loop, when the 
previous context and variable values are restored.

The FOREACH 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.

    [% users = {
	 tom   => 'Thomas',
	 dick  => 'Richard',
         larry => 'Lawrence',
       }
    %]

    [% FOREACH u = users %]
       * [% u.key %] : [% u.value %]
    [% END %]

Output:

       * dick : Richard
       * larry : Lawrence
       * tom : Thomas      

The NEXT directive starts the next iteration in the FOREACH loop.

    [% FOREACH user = userlist %]
       [% NEXT IF user.isguest %]
       Name: [% user.name %]    Email: [% user.email %]
    [% END %]

The LAST directive can be used to prematurely exit the loop.  BREAK is
also provided as an alias for LAST.

    [% FOREACH match = results.nsort('score').reverse %]
       [% LAST IF match.score < 50 %]
       [% match.score %] : [% match.url %]
    [% END %]

The FOREACH directive is implemented using the Template::Iterator
module.  A reference to the iterator object for a FOREACH directive is
implicitly available in the 'loop' variable.  The following methods 
can be called on the 'loop' iterator.

    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

See L<Template::Iterator> for further details.

Example:

    [% FOREACH item = [ 'foo', 'bar', 'baz' ] -%]
       [%- "<ul>\n" IF loop.first %]
       <li>[% loop.count %]/[% loop.size %]: [% item %]
       [%- "</ul>\n" IF loop.last %]
    [% END %]

Output:

    <ul>
    <li>1/3: foo
    <li>2/3: bar
    <li>3/3: baz
    </ul>

Note that the number() method is supported as an alias for count() for
backwards compatibility but may be deprecated in some future version.

Nested loops will work as expected, with the 'loop' variable correctly 
referencing the innermost loop and being restored to any previous 
value (i.e. an outer loop) at the end of the loop.

    [% FOREACH group = grouplist;
	   # loop => group iterator
           "Groups:\n" IF loop.first;

           FOREACH user = group.userlist;
               # loop => user iterator
	       "$loop.count: $user.name\n";
	   END;

	   # loop => group iterator
           "End of Groups\n" IF loop.last;
       END 
    %]

The 'iterator' 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 'loop'.  See Template::Plugin::Iterator for further
details.

    [% USE giter = iterator(grouplist) %]

    [% FOREACH group = giter %]
       [% FOREACH user = group.userlist %]
             user #[% loop.count %] in
             group [% giter.count %] is
             named [% user.name %]
       [% END %]
    [% END %]




=item WHILE

The WHILE directive can be used to repeatedly process a template block
while a conditional expression evaluates true.  The expression may 
be arbitrarily complex as per IF / UNLESS.

    [% WHILE total < 100 %]
       ...
       [% total = calculate_new_total %]
    [% END %]

An assignment can be enclosed in parenthesis to evaluate the assigned
value.

    [% WHILE (user = get_next_user_record) %]
       [% user.name %]
    [% END %]

The NEXT directive can be used to start the next iteration of a 
WHILE loop and BREAK can be used to exit the loop, both as per FOREACH.

The Template Toolkit uses a failsafe counter to prevent runaway WHILE
loops which would otherwise never terminate.  If the loop exceeds 1000
iterations then an 'undef' exception will be thrown, reporting the
error:

    WHILE loop terminated (> 1000 iterations)

The $Template::Directive::WHILE_MAX variable controls this behaviour
and can be set to a higher value if necessary.


=back

=head2 Filters, Plugins, Macros and Perl

=over 4


=item FILTER

The FILTER directive can be used to post-process the output of a
block.  A number of standard filters are provided with the Template
Toolkit.  The 'html' filter, for example, escapes the 'E<lt>', 'E<gt>'
and '&' characters to prevent them from being interpreted as HTML tags
or entity reference markers.

    [% FILTER html %]
       HTML text may have < and > characters embedded
       which you want converted to the correct HTML entities.
    [% END %]

output:

       HTML text may have &lt; and &gt; characters embedded
       which you want converted to the correct HTML entities.

The FILTER directive can also follow various other non-block directives.
For example:

    [% INCLUDE mytext FILTER html %]

The '|' character can also be used as an alias for 'FILTER'.

    [% INCLUDE mytext | html %]

Multiple filters can be chained together and will be called in sequence.

    [% INCLUDE mytext FILTER html FILTER html_para %]

or

    [% INCLUDE mytext | html | html_para %]

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 'html' filter is
an example of a static filter, implemented as:

    sub html_filter {
	my $text = shift;
    	for ($text) {
	    s/&/&amp;/g;
	    s/</&lt;/g;
	    s/>/&gt;/g;
    	}
	return $text;
    }

Dynamic filters can accept arguments which are specified when the filter
is called from a template.  The 'repeat' filter is such an example, 
accepting a numerical argument which specifies the number of times
that the input text should be repeated.

    [% FILTER repeat(3) %]blah [% END %]

output:

    blah blah blah

These are implemented as filter 'factories'.  The factory subroutine
is passed a reference to the current Template::Context object along
with any additional arguments specified.  It should then return a
subroutine reference (e.g. a closure) which implements the filter.
The 'repeat' filter factory is implemented like this:

    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;
	}
    }

The FILTERS option, described in L<Template::Manual::Config>, allows 
custom filters to be defined when a Template object is instantiated.  
The Template::Context define_filter() method allows further filters
to be defined at any time.

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.

    [% FILTER echo = repeat(2) %]
    Is there anybody out there?
    [% END %]

    [% FILTER echo %]
    Mother, should I build a wall?
    [% END %]

Output:

    Is there anybody out there?
    Is there anybody out there?

    Mother, should I build a wall?
    Mother, should I build a wall?

The FILTER directive automatically quotes the name of the filter.  As
with INCLUDE et al, you can use a variable to provide the name of the 
filter, prefixed by '$'.

    [% myfilter = 'html' %]
    [% FILTER $myfilter %]	# same as [% FILTER html %]
       ...
    [% END %]

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:

    my $vars = {
	myfilter => sub { return 'html' },
    };

template:

    [% FILTER $myfilter %]	# same as [% FILTER html %]
       ...
    [% END %]

To define a template variable that evaluates to a subroutine reference
that can be used by the FILTER 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.

    my $vars = {
	myfilter => sub { \&my_filter_sub },
    };

    sub my_filter_sub {
	my $text = shift;
	# do something
        return $text;
    }

template:

    [% FILTER $myfilter %]
       ...
    [% END %]

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.

    my $vars = {
	myfilter => bless(\&my_filter_sub, 'anything_you_like'),
    };

template:

    [% FILTER $myfilter %]	    
       ...
    [% END %]

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 PERL block within a template that is loaded via INCLUDE, 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 define_filter() method on the current Template::Context
object.

See L<Template::Manual::Filters> for a complete list of available filters,
their descriptions and examples of use.






=item USE

The USE directive can be used to load and initialise "plugin"
extension modules.

    [% USE myplugin %]

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 L<Template::Plugin>. 

The plugin name is case-sensitive and will be appended to the
PLUGIN_BASE value (default: 'Template::Plugin') to construct a full
module name.  Any periods, '.', in the name will be converted to '::'.

    [% USE MyPlugin %]     #  => Template::Plugin::MyPlugin
    [% USE Foo.Bar  %]     #  => Template::Plugin::Foo::Bar

Various standard plugins are included with the Template Toolkit (see 
below and L<Template::Manual::Plugins>).  These can be specified in lower
case and are mapped to the appropriate name.

    [% USE cgi   %]        # => Template::Plugin::CGI
    [% USE table %]        # => Template::Plugin::Table

Any additional parameters supplied in parenthesis after the plugin
name will be also be passed to the new() constructor.  A reference to
the current Template::Context object is always passed as the first
parameter.

    [% USE MyPlugin('foo', 123) %]

equivalent to:

    Template::Plugin::MyPlugin->new($context, 'foo', 123);

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.

    [% USE url('/cgi-bin/foo', mode='submit', debug=1) %]

equivalent to:

    Template::Plugin::URL->new($context, '/cgi-bin/foo'
			       { mode => 'submit', debug => 1 });

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:

    [% USE table(mydata, rows=3) %]

    [% FOREACH row = table.rows %]
       <tr>    
       [% FOREACH item = row %]
	  <td>[% item %]</td>
       [% END %]
       </tr>
    [% END %]

An alternative name may be provided for the plugin by which it can be 
referenced:

    [% USE scores = table(myscores, cols=5) %]

    [% FOREACH row = scores.rows %]
       ...
    [% END %]

You can use this approach to create multiple plugin objects with
different configurations.  This example shows how the 'format' plugin
is used to create sub-routines bound to variables for formatting text
as per printf().

    [% USE bold = format('<b>%s</b>') %]
    [% USE ital = format('<i>%s</i>') %]

    [% bold('This is bold')   %]
    [% ital('This is italic') %]

Output:

    <b>This is bold</b>
    <i>This is italic</i>

This next example shows how the URL plugin can be used to build
dynamic URLs from a base part and optional query parameters.

    [% USE mycgi = URL('/cgi-bin/foo.pl', debug=1) %]
    <a href="[% mycgi %]">...
    <a href="[% mycgi(mode='submit') %]"...

Output:

    <a href="/cgi-bin/foo.pl?debug=1">...
    <a href="/cgi-bin/foo.pl?mode=submit&debug=1">...

The CGI plugin is an example of one which delegates to another Perl
module.  In this this case, it is to Lincoln Stein's CGI.pm module.
All of the methods provided by CGI.pm are available via the plugin.

    [% 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 %]

Simon Matthews has written the DBI plugin which provides an interface
to Tim Bunce's DBI module (available from CPAN).  Here's a short
example:

    [% USE DBI('DBI:mSQL:mydbname') %]

    [% FOREACH user = DBI.query('SELECT * FROM users') %]
       [% user.id %] [% user.name %] [% user.etc.etc %]
    [% END %]

See L<Template::Manual::Plugins> for more information on the plugins
distributed with the toolkit or available from CPAN.

The LOAD_PERL 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 Template::Plugin::* or other module relative to some
PLUGIN_BASE) supports an object-oriented interface and a new()
constructor then it can be loaded and instantiated automatically.  The
following trivial example shows how the IO::File module might be used.

    [% USE file = IO.File('/tmp/mydata') %]

    [% WHILE (line = file.getline) %]
       <!-- [% line %] -->
    [% END %]






=item MACRO

The MACRO directive allows you to define a directive or directive block
which is then evaluated each time the macro is called. 

    [% MACRO header INCLUDE header %]

Calling the macro as:

    [% header %]

is then equivalent to:

    [% INCLUDE header %]

Macros can be passed named parameters when called.  These values remain 
local to the macro.

    [% header(title='Hello World') %]  

equivalent to:

    [% INCLUDE header title='Hello World' %]

A MACRO definition may include parameter names.  Values passed to the 
macros are then mapped to these local variables.  Other named parameters
may follow these.

    [% MACRO header(title) INCLUDE header %]

    [% header('Hello World') %]
    [% header('Hello World', bgcol='#123456') %]

equivalent to:

    [% INCLUDE header title='Hello World' %]
    [% INCLUDE header title='Hello World' bgcol='#123456# %]

A MACRO may precede any directive and must conform to the structure 
of the directive.

    [% MACRO header IF frames %]
       [% INCLUDE frames/header %]
    [% ELSE %]
       [% INCLUDE header %]
    [% END %]

    [% header %]

A MACRO may also be defined as an anonymous BLOCK.  The block will be
evaluated each time the macro is called. 

    [% MACRO header BLOCK %]
       ...content...
    [% END %]

    [% header %]






=item PERL

The PERL directive is used to mark the start of a block which contains
Perl code for evaluation.  The EVAL_PERL option must be enabled for Perl
code to be evaluated or a 'perl' exception will be thrown with the 
message 'EVAL_PERL not set'.

Perl code is evaluated in the Template::Perl package.  The $context
package variable contains a reference to the current Template::Context
object.  This can be used to access the functionality of the Template
Toolkit to process other templates, load plugins, filters, etc.
See L<Template::Context> for further details.

    [% PERL %]
       print $context->include('myfile');
    [% END %]

The $stash variable contains a reference to the top-level stash object
which manages template variables.  Through this, variable values can
be retrieved and updated.  See L<Template::Stash> for further details.

    [% PERL %]
       $stash->set(foo => 'bar');
       print "foo value: ", $stash->get('foo');
    [% END %]

Output
    foo value: bar

Output is generated from the PERL block by calling print().  Note that
the Template::Perl::PERLOUT handle is selected (tied to an output
buffer) instead of STDOUT.

    [% 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 %]

The PERL block may contain other template directives.  These are
processed before the Perl code is evaluated.

    [% name = 'Fred Smith' %]

    [% PERL %]
       print "[% name %]\n";
    [% END %]

Thus, the Perl code in the above example is evaluated as:

    print "Fred Smith\n";

Exceptions may be thrown from within PERL blocks via die() and will be
correctly caught by enclosing TRY blocks.

    [% TRY %]
       [% PERL %]
          die "nothing to live for\n";
       [% END %]
    [% CATCH %]
       error: [% error.info %]
    [% END %]

output:
       error: nothing to live for




=item RAWPERL

The Template Toolkit parser reads a source template and generates the
text of a Perl subroutine as output.  It then uses eval() to evaluate
it into a subroutine reference.  This subroutine is then called to
process the template, passing a reference to the current
Template::Context 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.

For example, a template such as:

    [% PROCESS header %]
    The [% animal %] sat on the [% location %]
    [% PROCESS footer %]

is converted into the following Perl subroutine definition:

    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;
    }

To examine the Perl code generated, such as in the above example, set
the $Template::Parser::DEBUG package variable to any true value.  You
can also set the $Template::Directive::PRETTY 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
STDERR on compilation (i.e. the first time a template is used).

    $Template::Parser::DEBUG = 1;
    $Template::Directive::PRETTY = 1;

    ...

    $template->process($file, $vars)
	|| die $template->error(), "\n";

The PERL ... END construct allows Perl code to be embedded into a
template (when the EVAL_PERL option is set), but it is evaluated at
"runtime" using eval() 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.  

The RAWPERL 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 RAWPERL blocks more
efficient than PERL blocks.

The downside is that you must code much closer to the metal.  Within
PERL blocks, you can call print() to generate some output.  RAWPERL
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 '$output' variable.

    [% PROCESS  header %]

    [% RAWPERL %]
       $output .= "Some output\n";
       ...
       $output .= "Some more output\n";
    [% END %]

The critical section of the generated subroutine for this example would 
then look something like:

    ...
    eval { BLOCK: {
	$output .=  $context->process('header');
        $output .=  "\n";
        $output .= "Some output\n";
	...
        $output .= "Some more output\n";
        $output .=  "\n";
    } };
    ...

As with PERL blocks, the $context and $stash references are pre-defined
and available for use within RAWPERL code. 


=back 

=head2 Exception Handling and Flow Control

=over 4


=item TRY / THROW / CATCH / FINAL

The Template Toolkit supports fully functional, nested exception
handling.  The TRY directive introduces an exception handling scope 
which continues until the matching END directive.  Any errors that 
occur within that block will be caught and can be handled by one
of the CATCH blocks defined.

    [% TRY %]
       ...blah...blah...
       [% CALL somecode %]
       ...etc...
       [% INCLUDE someblock %]
       ...and so on...
    [% CATCH %]
       An error occurred!
    [% END %]

Errors are raised as exceptions (objects of the Template::Exception 
class) and contain two fields, 'type' and 'info'.  The exception 
'type' can be any string containing letters, numbers, '_' or '.', and
is used to indicate the kind of error that occurred.  The 'info' field
contains an error message indicating what actually went wrong.  Within
a catch block, the exception object is aliased to the 'error' variable.
You can access the 'type' and 'info' fields directly.

    [% mydsn = 'dbi:MySQL:foobar' %]
    ...

    [% TRY %]
       [% USE DBI(mydsn) %]
    [% CATCH %]
       ERROR! Type: [% error.type %]
              Info: [% error.info %]
    [% END %]

output (assuming a non-existant database called 'foobar'):

    ERROR!  Type: DBI
            Info: Unknown database "foobar"

The 'error' variable can also be specified by itself and will return a 
string of the form "$type error - $info".

    ...
    [% CATCH %]
    ERROR: [% error %]
    [% END %]

output:

    ERROR: DBI error - Unknown database "foobar"

Each CATCH block may be specified with a particular exception type
denoting the kind of error that it should catch.  Multiple CATCH
blocks can be provided to handle different types of exception that may
be thrown in the TRY block.  A CATCH 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 
[% CATCH DEFAULT %].

    [% TRY %]
       [% INCLUDE myfile %]
       [% USE DBI(mydsn) %]
       [% CALL somecode %]
       ...
    [% CATCH file %]
       File Error! [% error.info %]
    [% CATCH DBI %]
       [% INCLUDE database/error.html %]
    [% CATCH %]
       [% error %]
    [% END %]

Remember that you can specify multiple directives within a single tag,
each delimited by ';'.  Thus, you might prefer to write your simple
CATCH blocks more succinctly as:

    [% TRY %]
       ...
    [% CATCH file; "File Error! $error.info" %]
    [% CATCH DBI;  INCLUDE database/error.html %]
    [% CATCH; error %]
    [% END %]

or even:

    [% TRY %]
       ...
    [% CATCH file ;
           "File Error! $error.info" ;
       CATCH DBI ;
	   INCLUDE database/error.html ;
       CATCH ;
	   error ;
       END
    %]

The DBI plugin throws exceptions of the 'DBI' type (in case that
wasn't already obvious).  The other specific exception caught here is
of the 'file' type.

A 'file' error 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 INCLUDE, PROCESS, INSERT or WRAPPER directive.
If 'myfile' can't be found in the example above, the [% INCLUDE myfile
%] directive will raise a 'file' exception which is then caught by the
[% CATCH file %] block, generating the output:

    File Error! myfile: not found

Note that the DEFAULT 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 DEFAULT file
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.

Uncaught exceptions (i.e. the TRY block doesn't have a type specific
or default CATCH handler) may be caught by enclosing TRY 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
process() method will return a false value to the caller.  The
relevant Template::Exception object can be retrieved by calling the
error() method.

    [% TRY %]
       ...
       [% TRY %]
          [% INCLUDE $user.header %]
       [% CATCH file %]
	  [% INCLUDE header %]
       [% END %]
       ...
    [% CATCH DBI %]
       [% INCLUDE database/error.html %]
    [% END %]

In this example, the inner TRY block is used to ensure that the first
INCLUDE directive works as expected.  We're using a variable to
provide the name of the template we want to include, user.header, and
it's possible this contains the name of a non-existant template, or
perhaps one containing invalid template directives.  If the INCLUDE fails
 with a 'file' error then we CATCH it in the inner block and INCLUDE
the default 'header' file instead.  Any DBI errors that occur within
the scope of the outer TRY block will be caught in the relevant CATCH
block, causing the 'database/error.html' 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.
e.g.

'database/error.html':

    <h2>Database Error</h2>
    A database error has occurred: [% error.info %]

You can also specify a FINAL block.  This is always processed
regardless of the outcome of the TRY and/or CATCH block.  If an
exception is uncaught then the FINAL block is processed before jumping
to the enclosing block or returning to the caller.

    [% TRY %]
       ...
    [% CATCH this %] 
       ...
    [% CATCH that %] 
       ...
    [% FINAL %]
       All done!
    [% END %]

The output from the TRY block is left intact up to the point where an
exception occurs.  For example, this template:

    [% TRY %]
       This gets printed 
       [% THROW food 'carrots' %]
       This doesn't
    [% CATCH food %]
       culinary delights: [% error.info %]
    [% END %]    

generates the following output:

    This gets printed
    culinary delights: carrots

The CLEAR directive can be used in a CATCH or FINAL block to clear
any output created in the TRY block.

    [% TRY %]
       This gets printed 
       [% THROW food 'carrots' %]
       This doesn't
    [% CATCH food %]
       [% CLEAR %]
       culinary delights: [% error.info %]
    [% END %]    

output:

    culinary delights: carrots

Exception types are hierarchical, with each level being separated by
the familiar dot operator.  A 'DBI.connect' exception is a more
specific kind of 'DBI' error.  Similarly, a 'myown.error.barf' is a
more specific kind of 'myown.error' type which itself is also a
'myown' error.  A CATCH handler that specifies a general exception
type (such as 'DBI' or 'myown.error') 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 CATCH handlers are
defined is irrelevant; a more specific handler will always catch an
exception in preference to a more generic or default one.

    [% TRY %]
       ...
    [% CATCH DBI ;
         INCLUDE database/error.html ;
       CATCH DBI.connect ;
         INCLUDE database/connect.html ;
       CATCH ; 
         INCLUDE error.html ;
       END
    %]

In this example, a 'DBI.connect' error has it's own handler, a more
general 'DBI' block is used for all other DBI or DBI.* errors and a 
default handler catches everything else.

Exceptions can be raised in a template using the THROW directive.  The
first parameter is the exception type which doesn't need to be quoted
(but can be, it's the same as INCLUDE) followed by the relevant error
message which can be any regular value such as a quoted string,
variable, etc.

    [% THROW food "Missing ingredients: $recipe.error" %]

    [% THROW user.login 'no user id: please login' %]

    [% THROW $myerror.type "My Error: $myerror.info" %]

It's also possible to specify additional positional or named 
parameters to the THROW directive if you want to pass more than 
just a simple message back as the error info field.  

    [% THROW food 'eggs' 'flour' msg='Missing Ingredients' %]

In this case, the error 'info' field will be a hash array containing
the named arguments, in this case 'msg' =E<gt> 'Missing Ingredients',
and an 'args' item which contains a list of the positional arguments, 
in this case 'eggs' and 'flour'.  The error 'type' field remains 
unchanged, here set to 'food'.

    [% CATCH food %]
       [% error.info.msg %]
       [% FOREACH item = error.info.args %]
          * [% item %]
       [% END %]
    [% END %]

This produces the output:

       Missing Ingredients
         * eggs
         * flour

In addition to specifying individual positional arguments as
[% error.info.args.n %], the 'info' hash contains keys directly 
pointing to the positional arguments, as a convenient shortcut.

    [% error.info.0 %]   # same as [% error.info.args.0 %]

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 die() passing a reference to a
Template::Exception object as the argument.  This will then be caught
by any enclosing TRY blocks from where the code was called.

    use Template::Exception;
    ...

    my $vars = {
	foo => sub {
	    # ... do something ...
	    die Template::Exception->new('myerr.naughty',
					 'Bad, bad error');
    	},
    };

template:

    [% TRY %]
       ...
       [% foo %]
       ...   
    [% CATCH myerr ;
         "Error: $error" ;
       END
    %]

output:

    Error: myerr.naughty error - Bad, bad error

The 'info' field can also be a reference to another object or data
structure, if required.

    die Template::Exception->new('myerror', { 
	module => 'foo.pl', 
	errors => [ 'bad permissions', 'naughty boy' ],
    });

Later, in a template:

    [% 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 %]

Generating the output:

       2 errors in foo.pl:
          bad permissions, naughty boy.

You can also call die() with a single string, as is common in much 
existing Perl code.  This will automatically be converted to an 
exception of the 'undef' type (that's the literal string 'undef', 
not the undefined value).  If the string isn't terminated with a 
newline then Perl will append the familiar " at $file line $line"
message.

    sub foo {
	# ... do something ...
	die "I'm sorry, Dave, I can't do that\n";
    }

If you're writing a plugin, or some extension code that has the
current Template::Context 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 throw() method.  You can pass it an
Template::Exception object reference, a pair of ($type, $info) parameters
or just an $info string to create an exception of 'undef' type.

    $context->throw($e);	    # exception object
    $context->throw('Denied');	    # 'undef' type
    $context->throw('user.passwd', 'Bad Password');







=item NEXT

The NEXT directive can be used to start the next iteration of a FOREACH 
or WHILE loop.

    [% FOREACH user = userlist %]
       [% NEXT IF user.isguest %]
       Name: [% user.name %]    Email: [% user.email %]
    [% END %]





=item LAST

The LAST directive can be used to prematurely exit a FOREACH or WHILE
loop.

    [% FOREACH user = userlist %]
       Name: [% user.name %]    Email: [% user.email %]
       [% LAST IF some.condition %]
    [% END %]

BREAK can also be used as an alias for LAST.




=item RETURN

The RETURN 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 INCLUDE, PROCESS or
WRAPPER directive.  If there is no enclosing template then the
Template process() method will return to the calling code with a 
true value.

    Before
    [% INCLUDE half_wit %]
    After
  
    [% BLOCK half_wit %]
    This is just half...
    [% RETURN %]
    ...a complete block
    [% END %]

output:

    Before
    This is just half...
    After




=item STOP

The STOP 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 process() method will return a
B<true> value to the caller.  This indicates that the template was
processed successfully according to the directives within it.

    [% IF something.terrible.happened %]
       [% INCLUDE fatal/error.html %]
       [% STOP %]
    [% END %]

    [% TRY %]
       [% USE DBI(mydsn) %]
       ...
    [% CATCH DBI.connect %]
       <p>Cannot connect to the database: [% error.info %]</p>
       <br>
       We apologise for the inconvenience.  The cleaning lady 
       has removed the server power to plug in her vacuum cleaner.
       Please try again later.
       </p>
       [% INCLUDE footer %]
       [% STOP %]
    [% END %]




=item CLEAR

The CLEAR 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 TRY block up to the point where the error occurred.

    [% 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 %]




=back

=head2 Miscellaneous

=over 4


=item META

The META 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 META variables).

    [% META
       title   = 'The Cat in the Hat'
       author  = 'Dr. Seuss'
       version = 1.23 
    %]

The 'template' variable contains a reference to the main template 
being processed.  These metadata items may be retrieved as attributes
of the template.  

    <h1>[% template.title %]</h1>
    <h2>[% template.author %]</h2>

The 'name' and 'modtime' metadata items are automatically defined for
each template to contain its name and modification time in seconds
since the epoch.

    [% USE date %]		# use Date plugin to format time
    ...
    [% template.name %] last modified
    at [% date.format(template.modtime) %]

The PRE_PROCESS and POST_PROCESS options allow common headers and 
footers to be added to all templates.  The 'template' reference is
correctly defined when these templates are processed, allowing headers
and footers to reference metadata items from the main template.

    $template = Template->new({
	PRE_PROCESS  => 'header',
	POST_PROCESS => 'footer',
    });

    $template->process('cat_in_hat');

header:

    <html>
    <head>
    <title>[% template.title %]</title>
    </head>
    <body>

cat_in_hat:

    [% META
       title   = 'The Cat in the Hat'
       author  = 'Dr. Seuss'
       version = 1.23 
       year    = 2000
    %]

    The cat in the hat sat on the mat.

footer:

    <hr>
    &copy; [% template.year %] [% template.author %]
    </body>
    </html>

The output generated from the above example is:

    <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>



=item TAGS

The TAGS directive can be used to set the START_TAG and END_TAG values
on a per-template file basis.

    [% TAGS <+ +> %]

    <+ INCLUDE header +>

The TAGS directive may also be used to set a named TAG_STYLE

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

See the TAGS and TAG_STYLE configuration options for further details.







=back

=head1 AUTHOR

Andy Wardley E<lt>abw@kfs.orgE<gt>

L<http://www.andywardley.com/|http://www.andywardley.com/>




=head1 VERSION

Template Toolkit version 2.06, released on 07 November 2001.

=head1 COPYRIGHT

  Copyright (C) 1996-2001 Andy Wardley.  All Rights Reserved.
  Copyright (C) 1998-2001 Canon Research Centre Europe Ltd.

This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

