PPI::Structure - The base class for Perl braced structures


PPI::Structure - The base class for Perl braced structures


  isa PPI::Node
      isa PPI::Element


PPI::Structure is the root class for all Perl bracing structures. This covers all forms of [ ... ] , { ... } , and ( ... ) brace types, and includes cases where only one half of the pair exist.

The class PPI::Structure itself is full abstract and no objects of that type should actually exist in the tree.

Elements vs Children

A PPI::Structure has an unusual existance. Unlike a the PPI::Document manpage or the PPI::Statement manpage, which both simply contain other elements, a structure both contains and consists of content.

That is, the brace tokens are not considered to be ``children'' of the structure, but are part of it.

In practice, this will mean that while the ->elements and ->tokens methods (and related) will return a list with the brace tokens at either end, the ->children method explicitly will not return the brace.


Excluding the transient the PPI::Structure::Unknown manpage that exists briefly inside the parser, there are six types of structure.

the PPI::Structure::List manpage

This covers all round braces used for function arguments, in foreach loops, literal lists, and braces used for precedence-ordering purposes.

the PPI::Structure::ForLoop manpage

Although not used for the foreach loop list, this is used for the special case of the round-brace three-part semicolon-seperated for loop expression (the traditional C style for loop).

the PPI::Structure::Condition manpage

This round-brace structure covers boolean conditional braces, such as for if and while blocks.

the PPI::Structure::Block manpage

This curly-brace and common structure is used for all form of code blocks. This includes those for if, do and similar, as well as grep, map, sort, sub and (labelled or anonymous) scoping blocks.

the PPI::Structure::Constructor manpage

This class covers brace structures used for the construction of anonymous ARRAY and HASH references.

the PPI::Structure::Subscript manpage

This class covers square-braces and curly-braces used after a -> pointer to access the subscript of an ARRAY or HASH.


PPI::Structure itself has very few methods. Most of the time, you will be working with the more generic the PPI::Element manpage or the PPI::Node manpage methods, or one of the methods that are subclass-specific.


For lack of better terminology (like ``open'' and ``close'') that has not already in use for some other more important purpose, the two individual braces for the structure are known within PPI as the ``start'' and ``finish'' braces (at least for method purposes).

The start method returns the start brace for the structure (i.e. the opening brace).

Returns the brace as a the PPI::Token::Structure manpage or undef if the structure does not have a starting brace.

Under normal parsing circumstances this should never occur, but may happen due to manipulation of the PDOM tree.


The finish method returns the finish brace for the structure (i.e. the closing brace).

Returns the brace as a the PPI::Token::Structure manpage or undef if the structure does not have a starting brace. This can be quite common if the document is not complete (for example, from an editor where the user may be halfway through typeing a subroutine).


The braces method is a utility method which returns the brace type.

Returns on of the three strings '[]', '{}', or '()', or undef on error (primarily not having a start brace, as mentioned above).


See the support section in the main module.


Adam Kennedy <adamk@cpan.org>


Copyright 2001 - 2006 Adam Kennedy.

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

The full text of the license can be found in the LICENSE file included with this module.

 PPI::Structure - The base class for Perl braced structures