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 here-
20 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
24 second section that should be something like a separate token, but
25 isn't because a string can span from above the here-doc content to
26 below it.
27 So when parsing, this is what we do.
29 Firstly, the PPI::Token::HereDoc object, does not represent the "<<"
31 operator, or the "END_FLAG", or the content, or even the terminator.
32 It represents all of them at once.
34 The token itself has only the declaration part as its "content".
36 # This is what the content of a HereDoc token is
38 <<FOO
39 # Or this
41 <<"FOO"
42 # Or even this
44 << 'FOO'
45 That is, the "operator", any whitespace separator, and the quoted or
47 bare terminator. So when you call the "content" method on a HereDoc
48 token, you get '<< "FOO"'.
49 As for the content and the terminator, when treated purely in "content"
51 terms they do not exist.
52 The content is made available with the "heredoc" method, and the name
54 of the terminator with the "terminator" method.
55 To make things work in the way you expect, PPI has to play some games
57 when doing line/column location calculation for tokens, and also during
58 the content parsing and generation processes.
59 Documents cannot simply by recreated by stitching together the token
61 contents, and involve a somewhat more expensive procedure, but the
62 extra expense should be relatively negligible unless you are doing huge
63 quantities of them.
64 Please note that due to the immature nature of PPI in general, we
66 expect "HereDocs" to be a rich (bad) source of corner-case bugs for
67 quite a while, but for the most part they should more or less DWYM.
68 Comparison to other string types
70 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
84 contents of the "HereDoc" object.
85 It returns the contents of the here-doc as a list of newline-terminated
87 strings. If called in scalar context, it returns the number of lines in
88 the here-doc, excluding the terminator line.
89 terminator
91 The "terminator" method returns the name of the terminating string for
92 the here-doc.
93 Returns the terminating string as an unescaped string (in the rare case
95 the terminator has an escaped quote in it).
96
98 - Implement PPI::Token::Quote interface compatibility
99 - Check CPAN for any use of the null here-doc or here-doc-in-s///e
101 - Add support for the null here-doc
103 - Add support for here-doc in s///e
105
107 See the support section in the main module.
108
110 Adam Kennedy <adamk@cpan.org>
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113 Copyright 2001 - 2011 Adam Kennedy.
114 This program is free software; you can redistribute it and/or modify it
116 under the same terms as Perl itself.
117 The full text of the license can be found in the LICENSE file included
119 with this module.
120perl v5.28.1 2017-06-22 PPI::Token::HereDoc(3)