1PPI::Token::HereDoc(3)User Contributed Perl DocumentationPPI::Token::HereDoc(3)
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6 PPI::Token::HereDoc - Token class for the here-doc
7
9 PPI::Token::HereDoc
10 isa PPI::Token
11 isa PPI::Element
12
14 Here-docs are incredibly handy when writing Perl, but incredibly tricky
15 when parsing it, primarily because they don't follow the general flow
16 of input.
17 They jump ahead and nab lines directly off the input buffer. Whitespace
19 and newlines may not matter in most Perl code, but they matter in
20 here-docs.
21 They are also tricky to store as an object. They look sort of like an
23 operator and a string, but they don't act like it. And they have a sec‐
24 ond section that should be something like a separate token, but isn't
25 because a strong can span from above the here-doc content to below it.
26 So when parsing, this is what we do.
28 Firstly, the PPI::Token::HereDoc object, does not represent the "<<"
30 operator, or the "END_FLAG", or the content, or even the terminator.
31 It represents all of them at once.
33 The token itself has only the declaration part as its "content".
35 # This is what the content of a HereDoc token is
37 <<FOO
38 # Or this
40 <<"FOO"
41 # Or even this
43 << 'FOO'
44 That is, the "operator", any whitespace separator, and the quoted or
46 bare terminator. So when you call the "content" method on a HereDoc
47 token, you get '<< "FOO"'.
48 As for the content and the terminator, when treated purely in "content"
50 terms they do not exist.
51 The content is made available with the "heredoc" method, and the name
53 of the terminator with the "terminator" method.
54 To make things work in the way you expect, PPI has to play some games
56 when doing line/column location calculation for tokens, and also during
57 the content parsing and generation processes.
58 Documents cannot simply by recreated by stitching together the token
60 contents, and involve a somewhat more expensive procedure, but the
61 extra expense should be relatively negligible unless you are doing huge
62 quantities of them.
63 Please note that due to the immature nature of PPI in general, we
65 expect "HereDocs" to be a rich (bad) source of corner-case bugs for
66 quite a while, but for the most part they should more or less DWYM.
67 Comparison to other string types
69 Although technically it can be considered a quote, for the time being
71 "HereDocs" are being treated as a completely separate "Token" subclass,
72 and will not be found in a search for PPI::Token::Quote or
73 "PPI::Token::QuoteLike objects".
74 This may change in the future, with it most likely to end up under
76 QuoteLike.
77
79 Although it has the standard set of "Token" methods, "HereDoc" objects
80 have a relatively large number of unique methods all of their own.
81 heredoc
83 The "heredoc" method is the authoritative method for accessing the con‐
85 tents of the "HereDoc" object.
86 It returns the contents of the here-doc as a list of newline-terminated
88 strings. If called in scalar context, it returns the number of lines in
89 the here-doc, excluding the terminator line.
90 terminator
92 The "terminator" method returns the name of the terminating string for
94 the here-doc.
95 Returns the terminating string as an unescaped string (in the rare case
97 the terminator has an escaped quote in it).
98
100 - Implement PPI::Token::Quote interface compatibility
101 - Check CPAN for any use of the null here-doc or here-doc-in-s///e
103 - Add support for the null here-doc
105 - Add support for here-doc in s///e
107
109 See the support section in the main module.
110
112 Adam Kennedy <adamk@cpan.org>
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115 Copyright 2001 - 2006 Adam Kennedy.
116 This program is free software; you can redistribute it and/or modify it
118 under the same terms as Perl itself.
119 The full text of the license can be found in the LICENSE file included
121 with this module.
122perl v5.8.8 2006-09-23 PPI::Token::HereDoc(3)