Text::Embed - Cleanly seperate unwieldy text from your source code
use Text::Embed use Text::Embed CODE|REGEX|SCALAR use Text::Embed CODE|REGEX|SCALAR, LIST
Code often requires chunks of text to operate - chunks not large enough to warrant extra file dependencies, but enough to make using quotes and heredocs' ugly.
A typical example might be code generators. The text itself is code, and as such is difficult to differentiate and maintain when it is embedded inside more code. Similarly, CGI scripts often include embedded HTML or SQL templates.
Text::Embed provides the programmer with a flexible way to store these portions of text in their namespace's __DATA__ handle - away from the logic - and access them through the package variable %DATA.
The general usage is expected to be suitable for a majority of cases:
use Text::Embed; foreach(keys %DATA) { print "$_ = $DATA{$_}\n"; } print $DATA{foo}; __DATA__ __foo__ yadda yadda yadda... __bar__ ee-aye ee-aye oh __baz__ woof woof
There are two stages to Text::Embed's execution - corresponding to the first and remaining arguments in its invocation.
use Text::Embed ( sub{ ... }, # parse key/values from DATA sub{ ... }, # process pairs ... # process pairs ); ... __DATA__ ...
By default, Text::Embed uses similar syntax to the __DATA__ token to seperate segments - a line consisting of two underscores surrounding an identifier. Of course, a suitable syntax depends on the text being embedded.
A REGEX or CODE reference can be passed as the first argument - in order to gain finer control of how __DATA__ is parsed:
use Text::Embed qr(<<<<<<<<(\w*?)>>>>>>>>);
A regular expression will be used in a call to split(). Any leading or trailing empty strings will be removed automatically.
split()
use Text::Embed sub{$_ = shift; ...} use Text::Embed &Some::Other::Function;
A subroutine will be passed a reference to the __DATA__ string. It should return a LIST of key-value pairs.
In the name of laziness, Text::Embed provides a couple of predefined formats:
Line-oriented __DATA__ like format:
__BAZ__ baz baz baz __FOO__ foo foo foo foo foo foo
CPP-like format (%DATA is readonly - can be used to define constants):
#define BAZ baz baz baz #define FOO foo foo foo foo foo foo
Line-agnostic CDATA-like format. Anything outside of tags is ignored.
<![BAZ[baz baz baz]]> <![FOO[ foo foo foo foo foo foo ]]>
After parsing, each key-value pair can be further processed by an arbitrary number of callbacks.
A common usage of this might be controlling how whitespace is represented in each segment. Text::Embed provides some likely defaults which operate on the hash values only.
Removes trailing or leading whitespace
Substitutes zero or more whitspace with a single <SPACE>
Removes trailing or leading blank lines, preserves all indentation
Removes trailing or leading blank lines, preserves unique indentation
Leave untouched
Same as :raw
If you need more control, CODE references or named subroutines can be invoked as necessary. At this point it is safe to rename or modify keys. Undefining a key removes the entry from %DATA.
For the sake of brevity, consider a module that has some embedded SQL. We can implement a processing callback that will prepare each statement, leaving %DATA full of ready to execute DBI statement handlers:
package Whatever; use DBI; use Text::Embed(':default', ':trim', 'prepare_sql'); my $dbh; sub prepare_sql { my ($k, $v) = @_; if(!$dbh) { $dbh = DBI->connect(...); } $$v = $dbh->prepare($$v); } sub get_widget { my $id = shift; my $sql = $DATA{select_widget}; $sql->execute($id); if($sql->rows) { ... } } __DATA__ __select_widget__ SELECT * FROM widgets WHERE widget_id = ?; __create_widget__ INSERT INTO widgets (widget_id,desc, price) VALUES (?,?,?); ..etc
Notice that each pair is passed by reference.
Several utility functions are available to aid implementing custom processing handlers. These are not exported into the callers namespace.
The first are equivalent to the default processing options:
use Text::Embed(':default',':trim'); use Text::Embed(':default', sub {Text::Embed::trim($_[1]);} );
use Text::Embed(':default',':compress'); use Text::Embed(':default', sub {Text::Embed::compress($_[1]);} );
use Text::Embed(':default',':block-indent'); use Text::Embed(':default', sub {Text::Embed::block($_[1]);} );
If a true value is passed as the second argument, then shared indentation is removed, ie :block-noindent.
If comments would make your segments easier to manage, Text::Embed provides defaults handlers for stripping common comment syntax - :strip-perl, :strip-c, :strip-cpp, :strip-xml.
use Text::Embed(':default',':strip-c'); use Text::Embed(':default', sub {Text::Embed::strip($_[1], '/\*', '\*/');} );
Strips all sequences between second and third arguments. The default arguments are '#' and '\n' respectively.
Typically, embedded text may well be some kind of template. Text::Embed provides rudimentary variable interpolation for simple templates. The default variable syntax is of the form $(foo):
$(foo)
my $tmpl = "Hello $(name)! Your age is $(age)\n"; my %vars = (name => 'World', age => 4.5 * (10 ** 9)); Text::Embed::interpolate(\$tmpl, \%vars); print $tmpl;
Any interpolation is done via a simple substitution. An additional regex argument should accomodate this appropriately, by capturing the necessary hashkey in $1:
$1
Text::Embed::interpolate(\$tmpl, \%vars, '<%(\S+)%>');
The most likely bugs related to using this module should manifest themselves as bad key/value error messages. There are two related causes:
bad key/value
It is important to realise that Text::Embed does not have its own comment syntax or preprocessor. Any parser that works using split() is likely to fail if comments precede the first segment. Comments should exist in the body of a segment - not preceding it.
If you are defining your own REGEX parser, make sure you understand how it works when used with split() - particularly if your syntax wraps your data. Consider using a subroutine for anything non-trivial.
If you employ REGEX parsers, use seperators that are significantly different - and well spaced - from your data, rather than relying on complicated regular expressions to escape pathological cases.
Bug reports and suggestions are most welcome.
Copyright (C) 2005 Chris McEwan - All rights reserved.
Chris McEwan <mcewan@cpan.org>
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
To install Text::Embed, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Text::Embed
CPAN shell
perl -MCPAN -e shell install Text::Embed
For more information on module installation, please visit the detailed CPAN module installation guide.