Petal::Utils(3) Useful template modifiers for Petal.


# install the default set of Petal modifiers:
use Petal::Utils;
# you can also install modifiers manually:
Petal::Utils->install( 'some_modifier', ':some_set' );
# see below for modifiers available & template syntax


The Petal::Utils package contains commonly used Petal modifiers (or plugins), and bundles them with an easy-to-use installation interface. By default, a set of modifiers are installed into Petal when you use this module. You can change which modifiers are installed by naming them after the use statement:

  # use the default set:
  use Petal::Utils qw( :default );
  # use the date set of modifiers:
  use Petal::Utils qw( :date );
  # use only named modifiers, plus the debug set:
  use Petal::Utils qw( UpperCase Date :debug );
  # don't install any modifiers
  use Petal::Utils qw();

You'll find a list of plugin sets throughout this document. You can also get a complete list by looking at the variable:


For details on how the plugins are installed, see the ``Advanced Petal'' section of the Petal documentation.


Each modifier is listed under the set it belongs to.


lowercase:, lc: $string
Make the entire string lowercase.

  <p tal:content="lc: $string">lower</p>
uppercase:, uc: $string
Make the entire string uppercase.

  <p tal:content="uc: $string">upper</p>
uc_first: $string
Make the first letter of the string uppercase.

  <p tal:content="uc_first: $string">uc_first</p>
substr: $string [offset] [length] [ellipsis]
Extract a substring from a string. Optionally add an ellipsis (...) to the end. See also, perldoc -f substr.

  <span petal:content="substr:$str">string</span>       # does nothing
  <span petal:content="substr:$str 2">string</span>     # cuts the first two chars
  <span petal:content="substr:$str 2 5">string</span>   # extracts chars 2-7
  <span petal:content="substr:$str 2 5 1">string with ellipsis</span>  # same as above and adds an ellipsis
printf: format list
The printf modifier acts exactly like Perl's sprintf function to print formatted strings.

  <p petal:content="printf:'%s' 'Astro'">Astro</p>
  <p petal:content="printf:'$%0.2f' '2.5'">$2.50</p>


date: $date
Convert a time() integer to a date string using Date::Format.

  <span tal:replace="date: $date">Jan  1 1970 01:00:01</span>
us_date: $date
Convert an international date stamp (e.g., yyyymmdd, yyyy-mm-dd, yyyy/mm/dd) to US format (mm/dd/yyyy).

  <p tal:content="us_date: $date">2003-09-05</p>


if: $expr1 then: $expr2 else: $expr3
Do an if/then/else test and return the value of the expression executed. Truthfulness of $expr1 is according to Perl (e.g., non-zero, non-empty string).

  <p tal:attributes="class if: on_a_page then: a_class else: another_class">
    Some text here...
or: $expr1 $expr2
Do a logical or. Truthfulness is according to Perl (e.g., non-zero, non-empty string).

  <p tal:if="or: $first $second">
    first or second = <span tal:replace="or: $first $second">or</span>
and: $expr1 $expr2
Do a logical and. Truthfulness is according to Perl (e.g., non-zero, non-empty string).

  first and second = <span tal:replace="and: $first $second">and</span>
equal:, eq: $expr1 $expr2
Test for equality. Numbers are compared with "==", strings with "eq". Truthfulness is according to Perl (e.g., non-zero, non-empty string).

  first eq second = <span tal:replace="eq: $first $second">equal</span>
like: $expr $regex
Test for equality to a regular expression (see perlre).

  name like regex = <span tal:replace="like: $name ^Will.+m">like</span>
decode, decode: expression search result [search result]... [default]
The decode function has the functionality of an IF-THEN-ELSE statement. A case-sensitive regex comparison is performed. All text strings must be enclosed in single quotes.

    'expression' is the value to compare.
    'search' is the value that is compared against expression.
    'result' is the value returned, if expression is equal to search.
    'default. is optional.  If no matches are found, the decode will return
      default.  If default is omitted, then the decode statement will return
      null (if no matches are found). 
  <p petal:content="decode:$str 'dog' 'Satchel'">100</p>  # if $str = dog, returns Satchel
  <p petal:content="decode:$str 'cat' 'Buckey' 'Satchel'">Astro</p>  # if $str = cat, returns Buckey, else Satchel


sort: $list
Sort the values in a list before returning it.

    <li tal:repeat="item sort: $array_ref">$item</li>
limit: $list count
Limit the values in a list before returning it.

    <li tal:repeat="item limit: $array_ref 2">$item</li>
limitr: $list count
Shuffle the list then limit the returned values to the specified count.

    <li tal:repeat="item limitr: $array_ref 2">$item</li>


keys: $hash
Return a list of keys for a hashref. Note: It appears that values cannot be accessed with dynamic keys. If you need the keys and values, use ``each:''.

    <li tal:repeat="key keys: $hash_ref"><span tal:replace="key">key</span></li>
each: $hash
Return a list of key/value pairs for a hashref.

    <li tal:repeat="item each: $hash_ref">
      <span tal:replace="item/key">key</span> => <span tal:replace="item/val">value</span>


uri_escape: $expr
Use URI::Escape's uri_escape() to escape the return value of the expression.

  <a href="http://foo/get.html?item=${uri_escape: item/key}">get $item/key</a>
create_href: $url [protocol]
Creates an absolute uri from a url with the given protocol (e.g., http, ftp --- do not include the protocol separators). If the url does not have the protocol included, it will be appended. If no protocol is given, 'http' will be used.

  <a petal:attr="href create_href:$url">HTTP Link</a>
  <a petal:attr="href create_href:$url ftp">FTP Link</a>


dump: $expr
Dump the data strcture of the value given.

  dump name: <span tal:replace="dump: name">dump</span>


At the time of writing, the following supersets were available:

   ':none'    => [],
   ':all'     => [qw( :default :hash :debug )],
   ':default' => [qw( :text :date :logic :list )],

See %Petal::Utils::PLUGIN_SET for an up-to-date list.


Contributions to the modifiers are welcome! You can suggest new modifiers to add to the suite. You will have better luck getting your modifier added by providing a module (see lib/Petal/Utils/ for an example), a patch to (with a modified PLUGIN_SET and documentation for your new modifier), and a test suite. All modifiers are subject to the discretion of the authors.


William McKee <[email protected]>, and Steve Purkis <[email protected]>


Copyright (c) 2003-2004 William McKee & Steve Purkis.

This module is free software and is distributed under the same license as Perl itself. Use it at your own risk.


Thanks to Jean-Michel Hiver for making Petal available to the Perl community.