Provided by: libtext-micromason-perl_2.16-1_all 
NAME
Text::MicroMason::HTMLMason - Simple Compiler for Mason-style Templating
SYNOPSIS
Create a MicroMason object to interpret the templates:
use Text::MicroMason;
my $mason = Text::MicroMason->new();
Use the standard compile and execute methods to parse and evalute templates:
print $mason->compile( text=>$template )->( @%args );
print $mason->execute( text=>$template, @args );
Mason syntax provides several ways to mix Perl into a text template:
<%args>
$name
</%args>
% if ( $name eq 'Dave' ) {
I'm sorry <% $name %>, I'm afraid I can't do that right now.
% } else {
<%perl>
my $hour = (localtime)[2];
my $daypart = ( $hour > 11 ) ? 'afternoon' : 'morning';
</%perl>
Good <% $daypart %>, <% $name %>!
% }
<& "includes/standard_footer.msn" &>
<%doc>
Here's a private developr comment describing this template.
</%doc>
DESCRIPTION
The Text::MicroMason::HTMLMason class provides lexer and assembler methods that allow
Text::MicroMason to handle most elements of HTML::Mason's template syntax.
Compatibility with HTML::Mason
HTML::Mason is a full-featured application server toolkit with many fatures, of which only
the templating functionality is emulated.
The following sets of HTML::Mason features are supported by Text::MicroMason:
• Template interpolation with <% expr %>
• Literal Perl lines with leading %
• Named %args, %perl, %once, %init, %cleanup, and %doc blocks
• The $m mason object, although with many fewer methods
• Expression filtering with |h and |u (via -Filter mixin)
The following sets of HTML::Mason features are not supported by Text::MicroMason:
• No %attr, %flag, %shared, %method, or %def blocks.
• No shared files like autohandler and dhandler.
• No $r request object. No mod_perl integration or configuration capability.
Contributed patches to add these features of HTML::Mason would be welcomed by the author.
Possible implemenations are described in Text::MicroMason::ToDo.
Private Methods
The following internal methods are used to implement the syntax described below.
lex_token
( $type, $value ) = $mason->lex_token();
Supports HTML::Mason's markup syntax.
Attempts to parse a token from the template text stored in the global $_ and returns a
token type and value. Returns an empty list if unable to parse further due to an
error.
assembler_rules()
Returns a hash of text elements used for Perl subroutine assembly. Used by assemble().
Supports HTML::Mason's named blocks of Perl code and documentation: %once, %init,
%cleanup, and %doc.
assemble_args
Called by assemble(), this method provides support for Mason's <%args> blocks.
TEMPLATE SYNTAX
Here's an example of Mason-style templating, taken from HTML::Mason:
% my $noun = 'World';
Hello <% $noun %>!
How are ya?
Interpreting this template with Text::MicroMason produces the same output as it would in
HTML::Mason:
Hello World!
How are ya?
Text::MicroMason::HTMLMason supports a syntax that is mostly a subset of that used by
HTML::Mason.
Template Markup
The following types of markup are recognized in template pages:
• literal_text
Anything not specifically parsed by one of the below rules is interpreted as literal
text.
• <% perl_expr %>
A Perl expression to be interpolated into the result.
For example, the following template text will return a scheduled greeting:
Good <% (localtime)[2]>11 ? 'afternoon' : 'morning' %>.
The block may span multiple lines and is scoped inside a "do" block, so it may contain
multiple Perl statements and it need not end with a semicolon.
Good <% my $h = (localtime)[2]; $h > 11 ? 'afternoon'
: 'morning' %>.
• % perl_code
Lines which begin with the % character, without any leading whitespace, may contain
arbitrary Perl code to be executed when encountering this portion of the template.
Their result is not interpolated into the result.
For example, the following template text will return a scheduled greeting:
% my $daypart = (localtime)[2]>11 ? 'afternoon' : 'morning';
Good <% $daypart %>.
The line may contain one or more statements. This code is is not placed in its own
block scope, so it should typically end with a semicolon; it can still open a spanning
block scope closed by a later perl block.
For example, the following template text will return one of two different messages
each time it's interpreted:
% if ( int rand 2 ) {
Hello World!
% } else {
Goodbye Cruel World!
% }
This also allows you to quickly comment out sections of a template by prefacing each
line with "% #".
This is equivalent to a <%perl>...</%perl> block.
• <& template_filename, arguments &>
Includes the results of a separate file containing MicroMason code, compiling it and
executing it with any arguments passed after the filename.
For example, we could place the following template text into an separate file:
Good <% $ARGS{hour} >11 ? 'afternoon' : 'morning' %>.
Assuming this file was named "greeting.msn", its results could be embedded within the
output of another script as follows:
<& "greeting.msn", hour => (localtime)[2] &>
• <%name> ... </%name>
A named block contains a span of text. The name at the start and end must match, and
must be one of the supported block names.
Depending on the name, performs one of the behaviors described in "Named Blocks".
Named Blocks
The following types of named blocks are supported:
• <%perl> perl_code </%perl>
Blocks surrounded by %perl tags may contain arbitrary Perl code. Their result is not
interpolated into the result.
These blocks may span multiple lines in your template file. For example, the below
template initializes a Perl variable inside a %perl block, and then interpolates the
result into a message.
<%perl>
my $count = join '', map "$_... ", ( 1 .. 9 );
</%perl>
Here are some numbers: <% $count %>
The code may contain one or more statements. This code is is not placed in its own
block scope, so it should typically end with a semicolon; it can still open a spanning
block scope closed by a later perl block.
For example, when the below template text is evaluated it will return a sequence of
digits:
Here are some numbers:
<%perl>
foreach my $digit ( 1 .. 9 ) {
</%perl>
<% $digit %>...
<%perl>
}
</%perl>
If the block is immediately followed by a line break, that break is discarded. These
blocks are not whitespace sensitive, so the template could be combined into a single
line if desired.
• <%args> variable => default </%args>
Defines a collection of variables to be initialized from named arguments passed to the
subroutine. Arguments are separated by one or more newlines, and may optionally be
followed by a default value. If no default value is provided, the argument is required
and the subroutine will croak if it is not provided.
For example, adding the following block to a template will initialize the three named
variables, and will fail if no "a => '...'" argument pair is passed:
<%args>
$a
@b => qw( foo bar baz )
%c => ()
</%args>
All the arguments are available as lexically scoped ("my") variables in the rest of
the component. Default expressions are evaluated in top-to-bottom order, and one
expression may reference an earlier one.
Only valid Perl variable names may be used in <%args> sections. Parameters with non-
valid variable names cannot be pre-declared and must be fetched manually out of the
%ARGS hash.
• <%init> perl_code </%init>
Similar to a %perl block, except that the code is moved up to the start of the
subroutine. This allows a template's initialization code to be moved to the end of the
file rather than requiring it to be at the top.
For example, the following template text will return a scheduled greeting:
Good <% $daypart %>.
<%init>
my $daypart = (localtime)[2]>11 ? 'afternoon' : 'morning';
</%init>
• <%cleanup> perl_code </%cleanup>
Similar to a %perl block, except that the code is moved down to the end of the
subroutine.
• <%once> perl_code </%once>
Similar to a %perl block, except that the code is executed once, when the template is
first compiled. (If a caller is using execute, this code will be run repeatedly, but
if they call compile and then invoke the resulting subroutine multiple times, the
%once code will only execute during the compilation step.)
This code does not have access to %ARGS and can not generate output. It can be used
to define constants, create persistent variables, or otherwise prepare the
environment.
For example, the following template text will return a increasing number each time it
is called:
<%once>
my $counter = 1000;
</%once>
The count is <% ++ $counter %>.
• <%doc> ... </%doc>
Provides space for template developer documentation or comments which are not included
in the output.
• <%text> ... </%text>
Produces literal text in the template output. Can be used to surround text that
contains other markup tags that should not be interpreted.
Equivalent to un-marked-up text.
The following types of named blocks are not supported by HTML::Mason, but are supported
here as a side-effect of the way the lexer and assembler are implemented.
• <%expr> ... </%expr>
A Perl expression to be interpolated into the result. The block may span multiple
lines and is scoped inside a "do" block, so it may contain multiple Perl statements
and it need not end with a semicolon.
Equivalent to the "<% ... %>" markup syntax.
• <%file> template_filename, arguments </%file>
Includes the results of a separate file containing MicroMason code, compiling it and
executing it with any arguments passed after the filename.
<%file> "greeting.msn", hour => (localtime)[2] </%file>
Equivalent to the "<& ... &>" markup syntax.
TEMPLATE CODING TECHNIQUES
Assembling Perl Source Code
When Text::MicroMason::Base assembles your lexed template into the equivalent Perl
subroutine, all of the literal (non-Perl) pieces are converted to "$_out->('text');"
statements, and the interpolated expressions are converted to "$_out->( do { expr } );"
statements. Code from %perl blocks and % lines are included exactly as-is.
Your code is eval'd in the "Text::MicroMason::Commands" package. The "use strict;" pragma
is enabled by default to simplify debugging.
Internal Sub-templates
You can create sub-templates within your template text by defining them as anonymous
subroutines and then calling them repeatedly. For example, the following template will
concatenate the results of the draw_item sub-template for each of three items:
<h1>We've Got Items!</h1>
% my $draw_item = sub {
<p><b><% $_[0] %></b>:<br>
<a href="/more?item=<% $_[0] %>">See more about <% $_[0] %>.</p>
% };
<%perl>
foreach my $item ( qw( Foo Bar Baz ) ) {
$draw_item->( $item );
}
</%perl>
Returning Text from Perl Blocks
To append to the result from within Perl code, call $_out->(text). (The $_out->() syntax
is unavailable in older versions of Perl; use the equivalent &$_out() syntax instead.)
For example, the below template text will return '123456789' when it is evaluated:
<%perl>
foreach my $digit ( 1 .. 9 ) {
$_out->( $digit )
}
</%perl>
You can also directly manipulate the value @OUT, which contains the accumulating result.
For example, the below template text will return an altered version of its message if a
true value for 'minor' is passed as an argument when the template is executed:
This is a funny joke.
% if ( $ARGS{minor} ) { foreach ( @OUT ) { tr[a-z][n-za-m] } }
SEE ALSO
For a full-featured web application system using this template syntax, see HTML::Mason.
For an overview of this distribution, see Text::MicroMason.
This is a subclass intended for use with Text::MicroMason::Base.
For distribution, installation, support, copyright and license information, see
Text::MicroMason::Docs::ReadMe.