++ed by:

26 PAUSE users
19 non-PAUSE users.

Adam Kennedy
and 1 contributors


PPI::Token::HereDoc - Token class for the here-doc


  isa PPI::Token
      isa PPI::Element


Here-docs are incredibly handy when writing Perl, but incredibly tricky when parsing it, primarily because they don't follow the general flow of input.

They jump ahead and nab lines directly off the input buffer. Whitespace and newlines may not matter in most Perl code, but they matter in here-docs.

They are also tricky to store as ab object. They look sort of like an operator and a string, but they don't act like it. And they have a second section that should be something like a separate token, but isn't because a strong can span from above the here-doc content to below it.

So when parsing, this is what we do.

Firstly, the PPI::Token::HereDoc object, does not represent the << operator, or the "END_FLAG", or the content, or even the terminator.

It represents all of them at once.

The token itself has a as it's "content" just the declaration part.

  # This is what the content of a HereDoc token is
  # Or this
  # Or even this
  <<      'FOO'

That is, the "operator", any whitespace seperator, and the quoted or bare terminator. When you call the content method on a HereDoc token, you get '<< "FOO"'.

As for the content and terminator, when treated purely in "content" terms they do not exist.

The content is made available with the heredoc method, and the name of the terminator with the terminator method.

To make things work in the way you expect, PPI has to play some games when doing line/column location calculation for tokens, and also during the content parsing and generation processes.

Document cannot simply by recreated by stitching together the token contents, and involve a somewhat more expensive procedure, but the extra expense should be relatively negligable unless you are doing huge quantaties of them.

Please note that due to the immature nature of PPI in general, we expect here-docs to be a rich (bad) source of corner-case bugs for quite a while, but for the most part they should more or less DWYM.

Comparison to other string types

Although technically it can be consider a quote, for the time being HereDocs are being treated as a completely seperate Token subclass, and will not be found in a search for PPI::Token::Quote or PPI::Token::QuoteLike objects.

This may change in the future, with it most likely to end up under QuoteLike.


Although it has the standard set of Token methods, HereDoc objects have a relatively large number of unique methods all of their own.


The heredoc method is the authorative method for accessing the contents of the here-doc.

It returns the contents of the here-doc as a list of newline-terminated strings. If called in scalar context, it returns the number of lines in the here-doc, excluding the terminator line.


The terminator method returns the name of the terminating string for the here-doc.

Returns the terminating string as an unescaped string (in the rare case the terminator has an escaped quote in it).


- Implement PPI::Token::Quote interface compatibility

- Check CPAN for any use of the null here-doc or here-doc-in-s///e

- Add support for the null here-doc

- Add support for here-doc in s///e


See the support section in the main module


Adam Kennedy (Maintainer), http://ali.as/, cpan@ali.as


Copyright (c) 2004 - 2005 Adam Kennedy. All rights reserved.

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.