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8a93676d SB |
1 | |
2 | =for comment | |
3 | This document is in Pod format. To read this, use a Pod formatter, | |
4 | like "perldoc perlpod". | |
5 | ||
a0d0e21e | 6 | =head1 NAME |
d74e8afc | 7 | X<POD> X<plain old documentation> |
a0d0e21e | 8 | |
8a93676d | 9 | perlpod - the Plain Old Documentation format |
a0d0e21e LW |
10 | |
11 | =head1 DESCRIPTION | |
12 | ||
8a93676d SB |
13 | Pod is a simple-to-use markup language used for writing documentation |
14 | for Perl, Perl programs, and Perl modules. | |
15 | ||
16 | Translators are available for converting Pod to various formats | |
17 | like plain text, HTML, man pages, and more. | |
18 | ||
19 | Pod markup consists of three basic kinds of paragraphs: | |
20 | L<ordinary|/"Ordinary Paragraph">, | |
21 | L<verbatim|/"Verbatim Paragraph">, and | |
22 | L<command|/"Command Paragraph">. | |
23 | ||
24 | ||
25 | =head2 Ordinary Paragraph | |
d74e8afc | 26 | X<POD, ordinary paragraph> |
8a93676d SB |
27 | |
28 | Most paragraphs in your documentation will be ordinary blocks | |
29 | of text, like this one. You can simply type in your text without | |
30 | any markup whatsoever, and with just a blank line before and | |
31 | after. When it gets formatted, it will undergo minimal formatting, | |
32 | like being rewrapped, probably put into a proportionally spaced | |
33 | font, and maybe even justified. | |
34 | ||
35 | You can use formatting codes in ordinary paragraphs, for B<bold>, | |
36 | I<italic>, C<code-style>, L<hyperlinks|perlfaq>, and more. Such | |
37 | codes are explained in the "L<Formatting Codes|/"Formatting Codes">" | |
38 | section, below. | |
39 | ||
a0d0e21e | 40 | |
b74bceb9 | 41 | =head2 Verbatim Paragraph |
d74e8afc | 42 | X<POD, verbatim paragraph> X<verbatim> |
a0d0e21e | 43 | |
8a93676d SB |
44 | Verbatim paragraphs are usually used for presenting a codeblock or |
45 | other text which does not require any special parsing or formatting, | |
46 | and which shouldn't be wrapped. | |
47 | ||
48 | A verbatim paragraph is distinguished by having its first character | |
49 | be a space or a tab. (And commonly, all its lines begin with spaces | |
50 | and/or tabs.) It should be reproduced exactly, with tabs assumed to | |
51 | be on 8-column boundaries. There are no special formatting codes, | |
52 | so you can't italicize or anything like that. A \ means \, and | |
53 | nothing else. | |
54 | ||
a0d0e21e | 55 | |
b74bceb9 | 56 | =head2 Command Paragraph |
d74e8afc | 57 | X<POD, command> |
b74bceb9 | 58 | |
8a93676d SB |
59 | A command paragraph is used for special treatment of whole chunks |
60 | of text, usually as headings or parts of lists. | |
61 | ||
62 | All command paragraphs (which are typically only one line long) start | |
63 | with "=", followed by an identifier, followed by arbitrary text that | |
64 | the command can use however it pleases. Currently recognized commands | |
65 | are | |
a0d0e21e | 66 | |
2757242d | 67 | =pod |
8a93676d SB |
68 | =head1 Heading Text |
69 | =head2 Heading Text | |
70 | =head3 Heading Text | |
71 | =head4 Heading Text | |
72 | =over indentlevel | |
73 | =item stuff | |
a0d0e21e | 74 | =back |
8a93676d SB |
75 | =begin format |
76 | =end format | |
77 | =for format text... | |
2757242d YO |
78 | =encoding type |
79 | =cut | |
8a93676d SB |
80 | |
81 | To explain them each in detail: | |
82 | ||
83 | =over | |
84 | ||
85 | =item C<=head1 I<Heading Text>> | |
d74e8afc ITB |
86 | X<=head1> X<=head2> X<=head3> X<=head4> |
87 | X<head1> X<head2> X<head3> X<head4> | |
cb1a09d0 | 88 | |
8a93676d | 89 | =item C<=head2 I<Heading Text>> |
b74bceb9 | 90 | |
8a93676d | 91 | =item C<=head3 I<Heading Text>> |
b74bceb9 | 92 | |
8a93676d | 93 | =item C<=head4 I<Heading Text>> |
b74bceb9 | 94 | |
8a93676d SB |
95 | Head1 through head4 produce headings, head1 being the highest |
96 | level. The text in the rest of this paragraph is the content of the | |
97 | heading. For example: | |
cb1a09d0 | 98 | |
8a93676d | 99 | =head2 Object Attributes |
b74bceb9 | 100 | |
8a93676d SB |
101 | The text "Object Attributes" comprises the heading there. (Note that |
102 | head3 and head4 are recent additions, not supported in older Pod | |
103 | translators.) The text in these heading commands can use | |
104 | formatting codes, as seen here: | |
b74bceb9 | 105 | |
8a93676d | 106 | =head2 Possible Values for C<$/> |
c6b85e5d | 107 | |
8a93676d SB |
108 | Such commands are explained in the |
109 | "L<Formatting Codes|/"Formatting Codes">" section, below. | |
c6b85e5d | 110 | |
8a93676d | 111 | =item C<=over I<indentlevel>> |
d74e8afc | 112 | X<=over> X<=item> X<=back> X<over> X<item> X<back> |
cb1a09d0 | 113 | |
8a93676d | 114 | =item C<=item I<stuff...>> |
b74bceb9 | 115 | |
8a93676d | 116 | =item C<=back> |
b74bceb9 | 117 | |
8a93676d SB |
118 | Item, over, and back require a little more explanation: "=over" starts |
119 | a region specifically for the generation of a list using "=item" | |
120 | commands, or for indenting (groups of) normal paragraphs. At the end | |
121 | of your list, use "=back" to end it. The I<indentlevel> option to | |
122 | "=over" indicates how far over to indent, generally in ems (where | |
123 | one em is the width of an "M" in the document's base font) or roughly | |
124 | comparable units; if there is no I<indentlevel> option, it defaults | |
125 | to four. (And some formatters may just ignore whatever I<indentlevel> | |
126 | you provide.) In the I<stuff> in C<=item I<stuff...>>, you may | |
127 | use formatting codes, as seen here: | |
b74bceb9 | 128 | |
8a93676d | 129 | =item Using C<$|> to Control Buffering |
cb1a09d0 | 130 | |
8a93676d SB |
131 | Such commands are explained in the |
132 | "L<Formatting Codes|/"Formatting Codes">" section, below. | |
b74bceb9 | 133 | |
8a93676d SB |
134 | Note also that there are some basic rules to using "=over" ... |
135 | "=back" regions: | |
b74bceb9 | 136 | |
8a93676d | 137 | =over |
b74bceb9 | 138 | |
8a93676d SB |
139 | =item * |
140 | ||
141 | Don't use "=item"s outside of an "=over" ... "=back" region. | |
142 | ||
143 | =item * | |
c7c9f956 | 144 | |
8a93676d SB |
145 | The first thing after the "=over" command should be an "=item", unless |
146 | there aren't going to be any items at all in this "=over" ... "=back" | |
147 | region. | |
148 | ||
149 | =item * | |
150 | ||
151 | Don't put "=headI<n>" commands inside an "=over" ... "=back" region. | |
152 | ||
153 | =item * | |
154 | ||
155 | And perhaps most importantly, keep the items consistent: either use | |
156 | "=item *" for all of them, to produce bullets; or use "=item 1.", | |
157 | "=item 2.", etc., to produce numbered lists; or use "=item foo", | |
158 | "=item bar", etc. -- namely, things that look nothing like bullets or | |
159 | numbers. | |
160 | ||
161 | If you start with bullets or numbers, stick with them, as | |
162 | formatters use the first "=item" type to decide how to format the | |
163 | list. | |
164 | ||
165 | =back | |
166 | ||
167 | =item C<=cut> | |
d74e8afc | 168 | X<=cut> X<cut> |
8a93676d SB |
169 | |
170 | To end a Pod block, use a blank line, | |
171 | then a line beginning with "=cut", and a blank | |
172 | line after it. This lets Perl (and the Pod formatter) know that | |
173 | this is where Perl code is resuming. (The blank line before the "=cut" | |
174 | is not technically necessary, but many older Pod processors require it.) | |
175 | ||
176 | =item C<=pod> | |
d74e8afc | 177 | X<=pod> X<pod> |
8a93676d SB |
178 | |
179 | The "=pod" command by itself doesn't do much of anything, but it | |
180 | signals to Perl (and Pod formatters) that a Pod block starts here. A | |
181 | Pod block starts with I<any> command paragraph, so a "=pod" command is | |
182 | usually used just when you want to start a Pod block with an ordinary | |
183 | paragraph or a verbatim paragraph. For example: | |
184 | ||
185 | =item stuff() | |
210b36aa | 186 | |
8a93676d | 187 | This function does stuff. |
210b36aa | 188 | |
8a93676d | 189 | =cut |
210b36aa | 190 | |
8a93676d SB |
191 | sub stuff { |
192 | ... | |
193 | } | |
210b36aa | 194 | |
8a93676d | 195 | =pod |
210b36aa | 196 | |
8a93676d | 197 | Remember to check its return value, as in: |
210b36aa AMS |
198 | |
199 | stuff() || die "Couldn't do stuff!"; | |
200 | ||
8a93676d SB |
201 | =cut |
202 | ||
203 | =item C<=begin I<formatname>> | |
d74e8afc | 204 | X<=begin> X<=end> X<=for> X<begin> X<end> X<for> |
8a93676d SB |
205 | |
206 | =item C<=end I<formatname>> | |
207 | ||
208 | =item C<=for I<formatname> I<text...>> | |
209 | ||
210 | For, begin, and end will let you have regions of text/code/data that | |
211 | are not generally interpreted as normal Pod text, but are passed | |
212 | directly to particular formatters, or are otherwise special. A | |
213 | formatter that can use that format will use the region, otherwise it | |
214 | will be completely ignored. | |
215 | ||
216 | A command "=begin I<formatname>", some paragraphs, and a | |
353c6505 | 217 | command "=end I<formatname>", mean that the text/data in between |
8a93676d SB |
218 | is meant for formatters that understand the special format |
219 | called I<formatname>. For example, | |
220 | ||
221 | =begin html | |
210b36aa | 222 | |
8a93676d | 223 | <hr> <img src="thang.png"> |
c7c9f956 | 224 | <p> This is a raw HTML paragraph </p> |
210b36aa | 225 | |
8a93676d SB |
226 | =end html |
227 | ||
228 | The command "=for I<formatname> I<text...>" | |
229 | specifies that the remainder of just this paragraph (starting | |
230 | right after I<formatname>) is in that special format. | |
231 | ||
232 | =for html <hr> <img src="thang.png"> | |
233 | <p> This is a raw HTML paragraph </p> | |
234 | ||
235 | This means the same thing as the above "=begin html" ... "=end html" | |
236 | region. | |
c7c9f956 | 237 | |
8a93676d SB |
238 | That is, with "=for", you can have only one paragraph's worth |
239 | of text (i.e., the text in "=foo targetname text..."), but with | |
240 | "=begin targetname" ... "=end targetname", you can have any amount | |
241 | of stuff inbetween. (Note that there still must be a blank line | |
242 | after the "=begin" command and a blank line before the "=end" | |
243 | command. | |
c7c9f956 KA |
244 | |
245 | Here are some examples of how to use these: | |
246 | ||
8a93676d SB |
247 | =begin html |
248 | ||
249 | <br>Figure 1.<br><IMG SRC="figure1.png"><br> | |
250 | ||
251 | =end html | |
252 | ||
253 | =begin text | |
254 | ||
255 | --------------- | |
256 | | foo | | |
257 | | bar | | |
258 | --------------- | |
a6006777 | 259 | |
8a93676d | 260 | ^^^^ Figure 1. ^^^^ |
a6006777 | 261 | |
8a93676d | 262 | =end text |
a6006777 | 263 | |
8a93676d SB |
264 | Some format names that formatters currently are known to accept |
265 | include "roff", "man", "latex", "tex", "text", and "html". (Some | |
266 | formatters will treat some of these as synonyms.) | |
a6006777 | 267 | |
8a93676d SB |
268 | A format name of "comment" is common for just making notes (presumably |
269 | to yourself) that won't appear in any formatted version of the Pod | |
270 | document: | |
a6006777 | 271 | |
8a93676d SB |
272 | =for comment |
273 | Make sure that all the available options are documented! | |
a6006777 | 274 | |
8a93676d SB |
275 | Some I<formatnames> will require a leading colon (as in |
276 | C<"=for :formatname">, or | |
277 | C<"=begin :formatname" ... "=end :formatname">), | |
278 | to signal that the text is not raw data, but instead I<is> Pod text | |
279 | (i.e., possibly containing formatting codes) that's just not for | |
280 | normal formatting (e.g., may not be a normal-use paragraph, but might | |
281 | be for formatting as a footnote). | |
c7c9f956 | 282 | |
a179871b | 283 | =item C<=encoding I<encodingname>> |
d74e8afc | 284 | X<=encoding> X<encoding> |
a179871b SB |
285 | |
286 | This command is used for declaring the encoding of a document. Most | |
287 | users won't need this; but if your encoding isn't US-ASCII or Latin-1, | |
288 | then put a C<=encoding I<encodingname>> command early in the document so | |
289 | that pod formatters will know how to decode the document. For | |
290 | I<encodingname>, use a name recognized by the L<Encode::Supported> | |
291 | module. Examples: | |
292 | ||
293 | =encoding utf8 | |
294 | ||
295 | =encoding koi8-r | |
296 | ||
297 | =encoding ShiftJIS | |
298 | ||
299 | =encoding big5 | |
300 | ||
8a93676d | 301 | =back |
c7c9f956 | 302 | |
8a93676d SB |
303 | And don't forget, when using any command, that the command lasts up |
304 | until the end of its I<paragraph>, not its line. So in the | |
305 | examples below, you can see that every command needs the blank | |
306 | line after it, to end its paragraph. | |
cb1a09d0 AD |
307 | |
308 | Some examples of lists include: | |
309 | ||
8a93676d SB |
310 | =over |
311 | ||
312 | =item * | |
313 | ||
314 | First item | |
315 | ||
316 | =item * | |
317 | ||
318 | Second item | |
319 | ||
320 | =back | |
321 | ||
322 | =over | |
323 | ||
324 | =item Foo() | |
325 | ||
326 | Description of Foo function | |
327 | ||
328 | =item Bar() | |
cb1a09d0 | 329 | |
8a93676d | 330 | Description of Bar function |
cb1a09d0 | 331 | |
8a93676d | 332 | =back |
cb1a09d0 | 333 | |
cb1a09d0 | 334 | |
8a93676d | 335 | =head2 Formatting Codes |
d74e8afc ITB |
336 | X<POD, formatting code> X<formatting code> |
337 | X<POD, interior sequence> X<interior sequence> | |
cb1a09d0 | 338 | |
8a93676d SB |
339 | In ordinary paragraphs and in some command paragraphs, various |
340 | formatting codes (a.k.a. "interior sequences") can be used: | |
cb1a09d0 | 341 | |
8a93676d SB |
342 | =for comment |
343 | "interior sequences" is such an opaque term. | |
344 | Prefer "formatting codes" instead. | |
cb1a09d0 | 345 | |
8a93676d | 346 | =over |
cb1a09d0 | 347 | |
8a93676d | 348 | =item C<IE<lt>textE<gt>> -- italic text |
d74e8afc | 349 | X<I> X<< IZ<><> >> X<POD, formatting code, italic> X<italic> |
cb1a09d0 | 350 | |
8a93676d SB |
351 | Used for emphasis ("C<be IE<lt>careful!E<gt>>") and parameters |
352 | ("C<redo IE<lt>LABELE<gt>>") | |
353 | ||
354 | =item C<BE<lt>textE<gt>> -- bold text | |
d74e8afc | 355 | X<B> X<< BZ<><> >> X<POD, formatting code, bold> X<bold> |
8a93676d SB |
356 | |
357 | Used for switches ("C<perl's BE<lt>-nE<gt> switch>"), programs | |
358 | ("C<some systems provide a BE<lt>chfnE<gt> for that>"), | |
359 | emphasis ("C<be BE<lt>careful!E<gt>>"), and so on | |
360 | ("C<and that feature is known as BE<lt>autovivificationE<gt>>"). | |
361 | ||
362 | =item C<CE<lt>codeE<gt>> -- code text | |
d74e8afc | 363 | X<C> X<< CZ<><> >> X<POD, formatting code, code> X<code> |
8a93676d SB |
364 | |
365 | Renders code in a typewriter font, or gives some other indication that | |
366 | this represents program text ("C<CE<lt>gmtime($^T)E<gt>>") or some other | |
367 | form of computerese ("C<CE<lt>drwxr-xr-xE<gt>>"). | |
368 | ||
369 | =item C<LE<lt>nameE<gt>> -- a hyperlink | |
d74e8afc | 370 | X<L> X<< LZ<><> >> X<POD, formatting code, hyperlink> X<hyperlink> |
8a93676d SB |
371 | |
372 | There are various syntaxes, listed below. In the syntaxes given, | |
373 | C<text>, C<name>, and C<section> cannot contain the characters | |
374 | '/' and '|'; and any '<' or '>' should be matched. | |
375 | ||
376 | =over | |
377 | ||
378 | =item * | |
cb1a09d0 | 379 | |
8a93676d | 380 | C<LE<lt>nameE<gt>> |
cb1a09d0 | 381 | |
8a93676d SB |
382 | Link to a Perl manual page (e.g., C<LE<lt>Net::PingE<gt>>). Note |
383 | that C<name> should not contain spaces. This syntax | |
384 | is also occasionally used for references to UNIX man pages, as in | |
385 | C<LE<lt>crontab(5)E<gt>>. | |
386 | ||
387 | =item * | |
388 | ||
389 | C<LE<lt>name/"sec"E<gt>> or C<LE<lt>name/secE<gt>> | |
390 | ||
391 | Link to a section in other manual page. E.g., | |
392 | C<LE<lt>perlsyn/"For Loops"E<gt>> | |
393 | ||
394 | =item * | |
395 | ||
396 | C<LE<lt>/"sec"E<gt>> or C<LE<lt>/secE<gt>> or C<LE<lt>"sec"E<gt>> | |
397 | ||
398 | Link to a section in this manual page. E.g., | |
399 | C<LE<lt>/"Object Methods"E<gt>> | |
a0d0e21e | 400 | |
b74bceb9 AB |
401 | =back |
402 | ||
8a93676d SB |
403 | A section is started by the named heading or item. For |
404 | example, C<LE<lt>perlvar/$.E<gt>> or C<LE<lt>perlvar/"$."E<gt>> both | |
405 | link to the section started by "C<=item $.>" in perlvar. And | |
406 | C<LE<lt>perlsyn/For LoopsE<gt>> or C<LE<lt>perlsyn/"For Loops"E<gt>> | |
407 | both link to the section started by "C<=head2 For Loops>" | |
408 | in perlsyn. | |
409 | ||
410 | To control what text is used for display, you | |
411 | use "C<LE<lt>text|...E<gt>>", as in: | |
412 | ||
413 | =over | |
414 | ||
415 | =item * | |
416 | ||
417 | C<LE<lt>text|nameE<gt>> | |
418 | ||
419 | Link this text to that manual page. E.g., | |
420 | C<LE<lt>Perl Error Messages|perldiagE<gt>> | |
421 | ||
422 | =item * | |
423 | ||
424 | C<LE<lt>text|name/"sec"E<gt>> or C<LE<lt>text|name/secE<gt>> | |
425 | ||
426 | Link this text to that section in that manual page. E.g., | |
8325efec | 427 | C<LE<lt>postfix "if"|perlsyn/"Statement Modifiers"E<gt>> |
8a93676d SB |
428 | |
429 | =item * | |
430 | ||
431 | C<LE<lt>text|/"sec"E<gt>> or C<LE<lt>text|/secE<gt>> | |
432 | or C<LE<lt>text|"sec"E<gt>> | |
433 | ||
434 | Link this text to that section in this manual page. E.g., | |
435 | C<LE<lt>the various attributes|/"Member Data"E<gt>> | |
436 | ||
437 | =back | |
438 | ||
439 | Or you can link to a web page: | |
440 | ||
441 | =over | |
442 | ||
443 | =item * | |
444 | ||
445 | C<LE<lt>scheme:...E<gt>> | |
446 | ||
447 | Links to an absolute URL. For example, | |
448 | C<LE<lt>http://www.perl.org/E<gt>>. But note | |
449 | that there is no corresponding C<LE<lt>text|scheme:...E<gt>> syntax, for | |
450 | various reasons. | |
451 | ||
452 | =back | |
453 | ||
454 | =item C<EE<lt>escapeE<gt>> -- a character escape | |
d74e8afc | 455 | X<E> X<< EZ<><> >> X<POD, formatting code, escape> X<escape> |
8a93676d SB |
456 | |
457 | Very similar to HTML/XML C<&I<foo>;> "entity references": | |
458 | ||
459 | =over | |
460 | ||
461 | =item * | |
462 | ||
463 | C<EE<lt>ltE<gt>> -- a literal E<lt> (less than) | |
464 | ||
465 | =item * | |
466 | ||
467 | C<EE<lt>gtE<gt>> -- a literal E<gt> (greater than) | |
468 | ||
469 | =item * | |
470 | ||
471 | C<EE<lt>verbarE<gt>> -- a literal | (I<ver>tical I<bar>) | |
472 | ||
473 | =item * | |
474 | ||
475 | C<EE<lt>solE<gt>> = a literal / (I<sol>idus) | |
476 | ||
477 | The above four are optional except in other formatting codes, | |
478 | notably C<LE<lt>...E<gt>>, and when preceded by a | |
479 | capital letter. | |
480 | ||
481 | =item * | |
482 | ||
483 | C<EE<lt>htmlnameE<gt>> | |
484 | ||
485 | Some non-numeric HTML entity name, such as C<EE<lt>eacuteE<gt>>, | |
486 | meaning the same thing as C<é> in HTML -- i.e., a lowercase | |
487 | e with an acute (/-shaped) accent. | |
488 | ||
489 | =item * | |
490 | ||
491 | C<EE<lt>numberE<gt>> | |
492 | ||
493 | The ASCII/Latin-1/Unicode character with that number. A | |
494 | leading "0x" means that I<number> is hex, as in | |
495 | C<EE<lt>0x201EE<gt>>. A leading "0" means that I<number> is octal, | |
496 | as in C<EE<lt>075E<gt>>. Otherwise I<number> is interpreted as being | |
497 | in decimal, as in C<EE<lt>181E<gt>>. | |
498 | ||
499 | Note that older Pod formatters might not recognize octal or | |
500 | hex numeric escapes, and that many formatters cannot reliably | |
501 | render characters above 255. (Some formatters may even have | |
502 | to use compromised renderings of Latin-1 characters, like | |
503 | rendering C<EE<lt>eacuteE<gt>> as just a plain "e".) | |
504 | ||
505 | =back | |
506 | ||
507 | =item C<FE<lt>filenameE<gt>> -- used for filenames | |
d74e8afc | 508 | X<F> X<< FZ<><> >> X<POD, formatting code, filename> X<filename> |
8a93676d SB |
509 | |
510 | Typically displayed in italics. Example: "C<FE<lt>.cshrcE<gt>>" | |
511 | ||
512 | =item C<SE<lt>textE<gt>> -- text contains non-breaking spaces | |
d74e8afc ITB |
513 | X<S> X<< SZ<><> >> X<POD, formatting code, non-breaking space> |
514 | X<non-breaking space> | |
8a93676d SB |
515 | |
516 | This means that the words in I<text> should not be broken | |
517 | across lines. Example: S<C<SE<lt>$x ? $y : $zE<gt>>>. | |
518 | ||
519 | =item C<XE<lt>topic nameE<gt>> -- an index entry | |
d74e8afc | 520 | X<X> X<< XZ<><> >> X<POD, formatting code, index entry> X<index entry> |
8a93676d SB |
521 | |
522 | This is ignored by most formatters, but some may use it for building | |
523 | indexes. It always renders as empty-string. | |
524 | Example: C<XE<lt>absolutizing relative URLsE<gt>> | |
525 | ||
526 | =item C<ZE<lt>E<gt>> -- a null (zero-effect) formatting code | |
d74e8afc | 527 | X<Z> X<< ZZ<><> >> X<POD, formatting code, null> X<null> |
8a93676d SB |
528 | |
529 | This is rarely used. It's one way to get around using an | |
530 | EE<lt>...E<gt> code sometimes. For example, instead of | |
531 | "C<NEE<lt>ltE<gt>3>" (for "NE<lt>3") you could write | |
532 | "C<NZE<lt>E<gt>E<lt>3>" (the "ZE<lt>E<gt>" breaks up the "N" and | |
533 | the "E<lt>" so they can't be considered | |
534 | the part of a (fictitious) "NE<lt>...E<gt>" code. | |
535 | ||
536 | =for comment | |
537 | This was formerly explained as a "zero-width character". But it in | |
538 | most parser models, it parses to nothing at all, as opposed to parsing | |
539 | as if it were a E<zwnj> or E<zwj>, which are REAL zero-width characters. | |
540 | So "width" and "character" are exactly the wrong words. | |
541 | ||
542 | =back | |
543 | ||
544 | Most of the time, you will need only a single set of angle brackets to | |
545 | delimit the beginning and end of formatting codes. However, | |
546 | sometimes you will want to put a real right angle bracket (a | |
547 | greater-than sign, '>') inside of a formatting code. This is particularly | |
548 | common when using a formatting code to provide a different font-type for a | |
549 | snippet of code. As with all things in Perl, there is more than | |
550 | one way to do it. One way is to simply escape the closing bracket | |
551 | using an C<E> code: | |
5455df32 GS |
552 | |
553 | C<$a E<lt>=E<gt> $b> | |
554 | ||
555 | This will produce: "C<$a E<lt>=E<gt> $b>" | |
556 | ||
8a93676d SB |
557 | A more readable, and perhaps more "plain" way is to use an alternate |
558 | set of delimiters that doesn't require a single ">" to be escaped. With | |
559 | the Pod formatters that are standard starting with perl5.5.660, doubled | |
560 | angle brackets ("<<" and ">>") may be used I<if and only if there is | |
561 | whitespace right after the opening delimiter and whitespace right | |
562 | before the closing delimiter!> For example, the following will | |
563 | do the trick: | |
d74e8afc | 564 | X<POD, formatting code, escaping with multiple brackets> |
5455df32 GS |
565 | |
566 | C<< $a <=> $b >> | |
567 | ||
568 | In fact, you can use as many repeated angle-brackets as you like so | |
569 | long as you have the same number of them in the opening and closing | |
570 | delimiters, and make sure that whitespace immediately follows the last | |
8a93676d SB |
571 | '<' of the opening delimiter, and immediately precedes the first '>' |
572 | of the closing delimiter. (The whitespace is ignored.) So the | |
573 | following will also work: | |
d74e8afc | 574 | X<POD, formatting code, escaping with multiple brackets> |
5455df32 GS |
575 | |
576 | C<<< $a <=> $b >>> | |
8a93676d | 577 | C<<<< $a <=> $b >>>> |
5455df32 | 578 | |
8a93676d SB |
579 | And they all mean exactly the same as this: |
580 | ||
581 | C<$a E<lt>=E<gt> $b> | |
582 | ||
583 | As a further example, this means that if you wanted to put these bits of | |
584 | code in C<C> (code) style: | |
585 | ||
586 | open(X, ">>thing.dat") || die $! | |
587 | $foo->bar(); | |
588 | ||
589 | you could do it like so: | |
590 | ||
591 | C<<< open(X, ">>thing.dat") || die $! >>> | |
592 | C<< $foo->bar(); >> | |
5455df32 | 593 | |
8a93676d SB |
594 | which is presumably easier to read than the old way: |
595 | ||
596 | C<open(X, "E<gt>E<gt>thing.dat") || die $!> | |
c58e3c1c | 597 | C<$foo-E<gt>bar();> |
8a93676d SB |
598 | |
599 | This is currently supported by pod2text (Pod::Text), pod2man (Pod::Man), | |
600 | and any other pod2xxx or Pod::Xxxx translators that use | |
601 | Pod::Parser 1.093 or later, or Pod::Tree 1.02 or later. | |
5455df32 | 602 | |
b74bceb9 | 603 | =head2 The Intent |
d74e8afc | 604 | X<POD, intent of> |
3141265f | 605 | |
8a93676d SB |
606 | The intent is simplicity of use, not power of expression. Paragraphs |
607 | look like paragraphs (block format), so that they stand out | |
608 | visually, and so that I could run them through C<fmt> easily to reformat | |
609 | them (that's F7 in my version of B<vi>, or Esc Q in my version of | |
610 | B<emacs>). I wanted the translator to always leave the C<'> and C<`> and | |
611 | C<"> quotes alone, in verbatim mode, so I could slurp in a | |
612 | working program, shift it over four spaces, and have it print out, er, | |
613 | verbatim. And presumably in a monospace font. | |
614 | ||
615 | The Pod format is not necessarily sufficient for writing a book. Pod | |
616 | is just meant to be an idiot-proof common source for nroff, HTML, | |
617 | TeX, and other markup languages, as used for online | |
618 | documentation. Translators exist for B<pod2text>, B<pod2html>, | |
619 | B<pod2man> (that's for nroff(1) and troff(1)), B<pod2latex>, and | |
620 | B<pod2fm>. Various others are available in CPAN. | |
621 | ||
a0d0e21e | 622 | |
b74bceb9 | 623 | =head2 Embedding Pods in Perl Modules |
d74e8afc | 624 | X<POD, embedding> |
4633a7c4 | 625 | |
8a93676d SB |
626 | You can embed Pod documentation in your Perl modules and scripts. |
627 | Start your documentation with an empty line, a "=head1" command at the | |
628 | beginning, and end it with a "=cut" command and an empty line. Perl | |
629 | will ignore the Pod text. See any of the supplied library modules for | |
630 | examples. If you're going to put your Pod at the end of the file, and | |
631 | you're using an __END__ or __DATA__ cut mark, make sure to put an | |
632 | empty line there before the first Pod command. | |
cb1a09d0 | 633 | |
8a93676d | 634 | __END__ |
cb1a09d0 | 635 | |
8a93676d | 636 | =head1 NAME |
cb1a09d0 | 637 | |
8a93676d | 638 | Time::Local - efficiently compute time from local and GMT time |
cb1a09d0 | 639 | |
8a93676d SB |
640 | Without that empty line before the "=head1", many translators wouldn't |
641 | have recognized the "=head1" as starting a Pod block. | |
cb1a09d0 | 642 | |
8a93676d | 643 | =head2 Hints for Writing Pod |
1294c5d8 | 644 | |
8a93676d | 645 | =over |
1294c5d8 JM |
646 | |
647 | =item * | |
d74e8afc | 648 | X<podchecker> X<POD, validating> |
1294c5d8 | 649 | |
8a93676d SB |
650 | The B<podchecker> command is provided for checking Pod syntax for errors |
651 | and warnings. For example, it checks for completely blank lines in | |
652 | Pod blocks and for unknown commands and formatting codes. You should | |
653 | still also pass your document through one or more translators and proofread | |
654 | the result, or print out the result and proofread that. Some of the | |
655 | problems found may be bugs in the translators, which you may or may not | |
656 | wish to work around. | |
1294c5d8 JM |
657 | |
658 | =item * | |
659 | ||
8a93676d | 660 | If you're more familiar with writing in HTML than with writing in Pod, you |
210b36aa | 661 | can try your hand at writing documentation in simple HTML, and converting |
8a93676d SB |
662 | it to Pod with the experimental L<Pod::HTML2Pod|Pod::HTML2Pod> module, |
663 | (available in CPAN), and looking at the resulting code. The experimental | |
664 | L<Pod::PXML|Pod::PXML> module in CPAN might also be useful. | |
665 | ||
666 | =item * | |
667 | ||
668 | Many older Pod translators require the lines before every Pod | |
669 | command and after every Pod command (including "=cut"!) to be a blank | |
670 | line. Having something like this: | |
671 | ||
672 | # - - - - - - - - - - - - | |
673 | =item $firecracker->boom() | |
210b36aa | 674 | |
8a93676d SB |
675 | This noisily detonates the firecracker object. |
676 | =cut | |
677 | sub boom { | |
678 | ... | |
679 | ||
680 | ...will make such Pod translators completely fail to see the Pod block | |
681 | at all. | |
682 | ||
683 | Instead, have it like this: | |
684 | ||
685 | # - - - - - - - - - - - - | |
210b36aa | 686 | |
8a93676d | 687 | =item $firecracker->boom() |
210b36aa | 688 | |
8a93676d | 689 | This noisily detonates the firecracker object. |
210b36aa | 690 | |
8a93676d | 691 | =cut |
210b36aa | 692 | |
8a93676d SB |
693 | sub boom { |
694 | ... | |
695 | ||
696 | =item * | |
697 | ||
698 | Some older Pod translators require paragraphs (including command | |
699 | paragraphs like "=head2 Functions") to be separated by I<completely> | |
700 | empty lines. If you have an apparently empty line with some spaces | |
701 | on it, this might not count as a separator for those translators, and | |
702 | that could cause odd formatting. | |
703 | ||
704 | =item * | |
1294c5d8 | 705 | |
8a93676d SB |
706 | Older translators might add wording around an LE<lt>E<gt> link, so that |
707 | C<LE<lt>Foo::BarE<gt>> may become "the Foo::Bar manpage", for example. | |
708 | So you shouldn't write things like C<the LE<lt>fooE<gt> | |
709 | documentation>, if you want the translated document to read sensibly | |
710 | -- instead write C<the LE<lt>Foo::Bar|Foo::BarE<gt> documentation> or | |
711 | C<LE<lt>the Foo::Bar documentation|Foo::BarE<gt>>, to control how the | |
712 | link comes out. | |
b74bceb9 | 713 | |
1294c5d8 JM |
714 | =item * |
715 | ||
8a93676d SB |
716 | Going past the 70th column in a verbatim block might be ungracefully |
717 | wrapped by some formatters. | |
1294c5d8 JM |
718 | |
719 | =back | |
720 | ||
cb1a09d0 AD |
721 | =head1 SEE ALSO |
722 | ||
8a93676d SB |
723 | L<perlpodspec>, L<perlsyn/"PODs: Embedded Documentation">, |
724 | L<perlnewmod>, L<perldoc>, L<pod2html>, L<pod2man>, L<podchecker>. | |
4633a7c4 | 725 | |
cb1a09d0 | 726 | =head1 AUTHOR |
a0d0e21e | 727 | |
8a93676d | 728 | Larry Wall, Sean M. Burke |
a0d0e21e | 729 | |
8a93676d | 730 | =cut |