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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 | |
684c7e37 BF |
101 | The text "Object Attributes" comprises the heading there. |
102 | The text in these heading commands can use formatting codes, as seen here: | |
b74bceb9 | 103 | |
8a93676d | 104 | =head2 Possible Values for C<$/> |
c6b85e5d | 105 | |
8a93676d SB |
106 | Such commands are explained in the |
107 | "L<Formatting Codes|/"Formatting Codes">" section, below. | |
c6b85e5d | 108 | |
8a93676d | 109 | =item C<=over I<indentlevel>> |
d74e8afc | 110 | X<=over> X<=item> X<=back> X<over> X<item> X<back> |
cb1a09d0 | 111 | |
8a93676d | 112 | =item C<=item I<stuff...>> |
b74bceb9 | 113 | |
8a93676d | 114 | =item C<=back> |
b74bceb9 | 115 | |
8a93676d SB |
116 | Item, over, and back require a little more explanation: "=over" starts |
117 | a region specifically for the generation of a list using "=item" | |
118 | commands, or for indenting (groups of) normal paragraphs. At the end | |
119 | of your list, use "=back" to end it. The I<indentlevel> option to | |
120 | "=over" indicates how far over to indent, generally in ems (where | |
121 | one em is the width of an "M" in the document's base font) or roughly | |
122 | comparable units; if there is no I<indentlevel> option, it defaults | |
123 | to four. (And some formatters may just ignore whatever I<indentlevel> | |
124 | you provide.) In the I<stuff> in C<=item I<stuff...>>, you may | |
125 | use formatting codes, as seen here: | |
b74bceb9 | 126 | |
8a93676d | 127 | =item Using C<$|> to Control Buffering |
cb1a09d0 | 128 | |
8a93676d SB |
129 | Such commands are explained in the |
130 | "L<Formatting Codes|/"Formatting Codes">" section, below. | |
b74bceb9 | 131 | |
8a93676d SB |
132 | Note also that there are some basic rules to using "=over" ... |
133 | "=back" regions: | |
b74bceb9 | 134 | |
8a93676d | 135 | =over |
b74bceb9 | 136 | |
8a93676d SB |
137 | =item * |
138 | ||
139 | Don't use "=item"s outside of an "=over" ... "=back" region. | |
140 | ||
141 | =item * | |
c7c9f956 | 142 | |
8a93676d SB |
143 | The first thing after the "=over" command should be an "=item", unless |
144 | there aren't going to be any items at all in this "=over" ... "=back" | |
145 | region. | |
146 | ||
147 | =item * | |
148 | ||
149 | Don't put "=headI<n>" commands inside an "=over" ... "=back" region. | |
150 | ||
151 | =item * | |
152 | ||
153 | And perhaps most importantly, keep the items consistent: either use | |
154 | "=item *" for all of them, to produce bullets; or use "=item 1.", | |
155 | "=item 2.", etc., to produce numbered lists; or use "=item foo", | |
ac036724 | 156 | "=item bar", etc.--namely, things that look nothing like bullets or |
8a93676d SB |
157 | numbers. |
158 | ||
159 | If you start with bullets or numbers, stick with them, as | |
160 | formatters use the first "=item" type to decide how to format the | |
161 | list. | |
162 | ||
163 | =back | |
164 | ||
165 | =item C<=cut> | |
d74e8afc | 166 | X<=cut> X<cut> |
8a93676d SB |
167 | |
168 | To end a Pod block, use a blank line, | |
169 | then a line beginning with "=cut", and a blank | |
170 | line after it. This lets Perl (and the Pod formatter) know that | |
171 | this is where Perl code is resuming. (The blank line before the "=cut" | |
172 | is not technically necessary, but many older Pod processors require it.) | |
173 | ||
174 | =item C<=pod> | |
d74e8afc | 175 | X<=pod> X<pod> |
8a93676d SB |
176 | |
177 | The "=pod" command by itself doesn't do much of anything, but it | |
178 | signals to Perl (and Pod formatters) that a Pod block starts here. A | |
179 | Pod block starts with I<any> command paragraph, so a "=pod" command is | |
180 | usually used just when you want to start a Pod block with an ordinary | |
181 | paragraph or a verbatim paragraph. For example: | |
182 | ||
183 | =item stuff() | |
210b36aa | 184 | |
8a93676d | 185 | This function does stuff. |
210b36aa | 186 | |
8a93676d | 187 | =cut |
210b36aa | 188 | |
8a93676d SB |
189 | sub stuff { |
190 | ... | |
191 | } | |
210b36aa | 192 | |
8a93676d | 193 | =pod |
210b36aa | 194 | |
8a93676d | 195 | Remember to check its return value, as in: |
210b36aa AMS |
196 | |
197 | stuff() || die "Couldn't do stuff!"; | |
198 | ||
8a93676d SB |
199 | =cut |
200 | ||
201 | =item C<=begin I<formatname>> | |
d74e8afc | 202 | X<=begin> X<=end> X<=for> X<begin> X<end> X<for> |
8a93676d SB |
203 | |
204 | =item C<=end I<formatname>> | |
205 | ||
206 | =item C<=for I<formatname> I<text...>> | |
207 | ||
208 | For, begin, and end will let you have regions of text/code/data that | |
209 | are not generally interpreted as normal Pod text, but are passed | |
210 | directly to particular formatters, or are otherwise special. A | |
211 | formatter that can use that format will use the region, otherwise it | |
212 | will be completely ignored. | |
213 | ||
214 | A command "=begin I<formatname>", some paragraphs, and a | |
353c6505 | 215 | command "=end I<formatname>", mean that the text/data in between |
8a93676d SB |
216 | is meant for formatters that understand the special format |
217 | called I<formatname>. For example, | |
218 | ||
219 | =begin html | |
210b36aa | 220 | |
8a93676d | 221 | <hr> <img src="thang.png"> |
c7c9f956 | 222 | <p> This is a raw HTML paragraph </p> |
210b36aa | 223 | |
8a93676d SB |
224 | =end html |
225 | ||
226 | The command "=for I<formatname> I<text...>" | |
227 | specifies that the remainder of just this paragraph (starting | |
228 | right after I<formatname>) is in that special format. | |
229 | ||
230 | =for html <hr> <img src="thang.png"> | |
231 | <p> This is a raw HTML paragraph </p> | |
232 | ||
233 | This means the same thing as the above "=begin html" ... "=end html" | |
234 | region. | |
c7c9f956 | 235 | |
8a93676d SB |
236 | That is, with "=for", you can have only one paragraph's worth |
237 | of text (i.e., the text in "=foo targetname text..."), but with | |
238 | "=begin targetname" ... "=end targetname", you can have any amount | |
1cecf2c0 | 239 | of stuff in between. (Note that there still must be a blank line |
8a93676d | 240 | after the "=begin" command and a blank line before the "=end" |
943fc58e | 241 | command.) |
c7c9f956 KA |
242 | |
243 | Here are some examples of how to use these: | |
244 | ||
8a93676d SB |
245 | =begin html |
246 | ||
247 | <br>Figure 1.<br><IMG SRC="figure1.png"><br> | |
248 | ||
249 | =end html | |
250 | ||
251 | =begin text | |
252 | ||
253 | --------------- | |
254 | | foo | | |
255 | | bar | | |
256 | --------------- | |
a6006777 | 257 | |
8a93676d | 258 | ^^^^ Figure 1. ^^^^ |
a6006777 | 259 | |
8a93676d | 260 | =end text |
a6006777 | 261 | |
8a93676d SB |
262 | Some format names that formatters currently are known to accept |
263 | include "roff", "man", "latex", "tex", "text", and "html". (Some | |
264 | formatters will treat some of these as synonyms.) | |
a6006777 | 265 | |
8a93676d SB |
266 | A format name of "comment" is common for just making notes (presumably |
267 | to yourself) that won't appear in any formatted version of the Pod | |
268 | document: | |
a6006777 | 269 | |
8a93676d SB |
270 | =for comment |
271 | Make sure that all the available options are documented! | |
a6006777 | 272 | |
8a93676d SB |
273 | Some I<formatnames> will require a leading colon (as in |
274 | C<"=for :formatname">, or | |
275 | C<"=begin :formatname" ... "=end :formatname">), | |
276 | to signal that the text is not raw data, but instead I<is> Pod text | |
277 | (i.e., possibly containing formatting codes) that's just not for | |
278 | normal formatting (e.g., may not be a normal-use paragraph, but might | |
279 | be for formatting as a footnote). | |
c7c9f956 | 280 | |
a179871b | 281 | =item C<=encoding I<encodingname>> |
d74e8afc | 282 | X<=encoding> X<encoding> |
a179871b SB |
283 | |
284 | This command is used for declaring the encoding of a document. Most | |
285 | users won't need this; but if your encoding isn't US-ASCII or Latin-1, | |
286 | then put a C<=encoding I<encodingname>> command early in the document so | |
287 | that pod formatters will know how to decode the document. For | |
288 | I<encodingname>, use a name recognized by the L<Encode::Supported> | |
289 | module. Examples: | |
290 | ||
291 | =encoding utf8 | |
292 | ||
293 | =encoding koi8-r | |
f703fc96 | 294 | |
a179871b | 295 | =encoding ShiftJIS |
f703fc96 | 296 | |
a179871b SB |
297 | =encoding big5 |
298 | ||
7a9a6fa1 DJ |
299 | C<=encoding> affects the whole document, and must occur only once. |
300 | ||
e023b52d KW |
301 | =back |
302 | ||
303 | And don't forget, all commands but C<=encoding> last up | |
8a93676d SB |
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 | |
556e7d6c KW |
306 | line after it, to end its paragraph. (And some older Pod translators |
307 | may require the C<=encoding> line to have a following blank line as | |
308 | well, even though it should be legal to omit.) | |
cb1a09d0 AD |
309 | |
310 | Some examples of lists include: | |
311 | ||
8a93676d SB |
312 | =over |
313 | ||
314 | =item * | |
315 | ||
316 | First item | |
317 | ||
318 | =item * | |
319 | ||
320 | Second item | |
321 | ||
322 | =back | |
323 | ||
324 | =over | |
325 | ||
326 | =item Foo() | |
327 | ||
328 | Description of Foo function | |
329 | ||
330 | =item Bar() | |
cb1a09d0 | 331 | |
8a93676d | 332 | Description of Bar function |
cb1a09d0 | 333 | |
8a93676d | 334 | =back |
cb1a09d0 | 335 | |
cb1a09d0 | 336 | |
8a93676d | 337 | =head2 Formatting Codes |
d74e8afc ITB |
338 | X<POD, formatting code> X<formatting code> |
339 | X<POD, interior sequence> X<interior sequence> | |
cb1a09d0 | 340 | |
8a93676d SB |
341 | In ordinary paragraphs and in some command paragraphs, various |
342 | formatting codes (a.k.a. "interior sequences") can be used: | |
cb1a09d0 | 343 | |
8a93676d SB |
344 | =for comment |
345 | "interior sequences" is such an opaque term. | |
346 | Prefer "formatting codes" instead. | |
cb1a09d0 | 347 | |
8a93676d | 348 | =over |
cb1a09d0 | 349 | |
8a93676d | 350 | =item C<IE<lt>textE<gt>> -- italic text |
d74e8afc | 351 | X<I> X<< IZ<><> >> X<POD, formatting code, italic> X<italic> |
cb1a09d0 | 352 | |
8a93676d SB |
353 | Used for emphasis ("C<be IE<lt>careful!E<gt>>") and parameters |
354 | ("C<redo IE<lt>LABELE<gt>>") | |
355 | ||
356 | =item C<BE<lt>textE<gt>> -- bold text | |
d74e8afc | 357 | X<B> X<< BZ<><> >> X<POD, formatting code, bold> X<bold> |
8a93676d SB |
358 | |
359 | Used for switches ("C<perl's BE<lt>-nE<gt> switch>"), programs | |
360 | ("C<some systems provide a BE<lt>chfnE<gt> for that>"), | |
361 | emphasis ("C<be BE<lt>careful!E<gt>>"), and so on | |
362 | ("C<and that feature is known as BE<lt>autovivificationE<gt>>"). | |
363 | ||
364 | =item C<CE<lt>codeE<gt>> -- code text | |
d74e8afc | 365 | X<C> X<< CZ<><> >> X<POD, formatting code, code> X<code> |
8a93676d SB |
366 | |
367 | Renders code in a typewriter font, or gives some other indication that | |
368 | this represents program text ("C<CE<lt>gmtime($^T)E<gt>>") or some other | |
369 | form of computerese ("C<CE<lt>drwxr-xr-xE<gt>>"). | |
370 | ||
371 | =item C<LE<lt>nameE<gt>> -- a hyperlink | |
d74e8afc | 372 | X<L> X<< LZ<><> >> X<POD, formatting code, hyperlink> X<hyperlink> |
8a93676d SB |
373 | |
374 | There are various syntaxes, listed below. In the syntaxes given, | |
375 | C<text>, C<name>, and C<section> cannot contain the characters | |
376 | '/' and '|'; and any '<' or '>' should be matched. | |
377 | ||
378 | =over | |
379 | ||
380 | =item * | |
cb1a09d0 | 381 | |
8a93676d | 382 | C<LE<lt>nameE<gt>> |
cb1a09d0 | 383 | |
8a93676d SB |
384 | Link to a Perl manual page (e.g., C<LE<lt>Net::PingE<gt>>). Note |
385 | that C<name> should not contain spaces. This syntax | |
e1020413 | 386 | is also occasionally used for references to Unix man pages, as in |
8a93676d SB |
387 | C<LE<lt>crontab(5)E<gt>>. |
388 | ||
389 | =item * | |
390 | ||
391 | C<LE<lt>name/"sec"E<gt>> or C<LE<lt>name/secE<gt>> | |
392 | ||
393 | Link to a section in other manual page. E.g., | |
394 | C<LE<lt>perlsyn/"For Loops"E<gt>> | |
395 | ||
396 | =item * | |
397 | ||
b41aadf2 | 398 | C<LE<lt>/"sec"E<gt>> or C<LE<lt>/secE<gt>> |
8a93676d SB |
399 | |
400 | Link to a section in this manual page. E.g., | |
401 | C<LE<lt>/"Object Methods"E<gt>> | |
a0d0e21e | 402 | |
b74bceb9 AB |
403 | =back |
404 | ||
8a93676d SB |
405 | A section is started by the named heading or item. For |
406 | example, C<LE<lt>perlvar/$.E<gt>> or C<LE<lt>perlvar/"$."E<gt>> both | |
407 | link to the section started by "C<=item $.>" in perlvar. And | |
408 | C<LE<lt>perlsyn/For LoopsE<gt>> or C<LE<lt>perlsyn/"For Loops"E<gt>> | |
409 | both link to the section started by "C<=head2 For Loops>" | |
410 | in perlsyn. | |
411 | ||
412 | To control what text is used for display, you | |
413 | use "C<LE<lt>text|...E<gt>>", as in: | |
414 | ||
415 | =over | |
416 | ||
417 | =item * | |
418 | ||
419 | C<LE<lt>text|nameE<gt>> | |
420 | ||
421 | Link this text to that manual page. E.g., | |
422 | C<LE<lt>Perl Error Messages|perldiagE<gt>> | |
423 | ||
424 | =item * | |
425 | ||
426 | C<LE<lt>text|name/"sec"E<gt>> or C<LE<lt>text|name/secE<gt>> | |
427 | ||
428 | Link this text to that section in that manual page. E.g., | |
8325efec | 429 | C<LE<lt>postfix "if"|perlsyn/"Statement Modifiers"E<gt>> |
8a93676d SB |
430 | |
431 | =item * | |
432 | ||
433 | C<LE<lt>text|/"sec"E<gt>> or C<LE<lt>text|/secE<gt>> | |
434 | or C<LE<lt>text|"sec"E<gt>> | |
435 | ||
436 | Link this text to that section in this manual page. E.g., | |
437 | C<LE<lt>the various attributes|/"Member Data"E<gt>> | |
438 | ||
439 | =back | |
440 | ||
441 | Or you can link to a web page: | |
442 | ||
443 | =over | |
444 | ||
445 | =item * | |
446 | ||
447 | C<LE<lt>scheme:...E<gt>> | |
448 | ||
f6e963e4 RS |
449 | C<LE<lt>text|scheme:...E<gt>> |
450 | ||
451 | Links to an absolute URL. For example, C<LE<lt>http://www.perl.org/E<gt>> or | |
452 | C<LE<lt>The Perl Home Page|http://www.perl.org/E<gt>>. | |
8a93676d SB |
453 | |
454 | =back | |
455 | ||
456 | =item C<EE<lt>escapeE<gt>> -- a character escape | |
d74e8afc | 457 | X<E> X<< EZ<><> >> X<POD, formatting code, escape> X<escape> |
8a93676d SB |
458 | |
459 | Very similar to HTML/XML C<&I<foo>;> "entity references": | |
460 | ||
461 | =over | |
462 | ||
463 | =item * | |
464 | ||
465 | C<EE<lt>ltE<gt>> -- a literal E<lt> (less than) | |
466 | ||
467 | =item * | |
468 | ||
469 | C<EE<lt>gtE<gt>> -- a literal E<gt> (greater than) | |
470 | ||
471 | =item * | |
472 | ||
473 | C<EE<lt>verbarE<gt>> -- a literal | (I<ver>tical I<bar>) | |
474 | ||
475 | =item * | |
476 | ||
1f1448d9 | 477 | C<EE<lt>solE<gt>> -- a literal / (I<sol>idus) |
8a93676d SB |
478 | |
479 | The above four are optional except in other formatting codes, | |
480 | notably C<LE<lt>...E<gt>>, and when preceded by a | |
481 | capital letter. | |
482 | ||
483 | =item * | |
484 | ||
485 | C<EE<lt>htmlnameE<gt>> | |
486 | ||
487 | Some non-numeric HTML entity name, such as C<EE<lt>eacuteE<gt>>, | |
488 | meaning the same thing as C<é> in HTML -- i.e., a lowercase | |
489 | e with an acute (/-shaped) accent. | |
490 | ||
491 | =item * | |
492 | ||
493 | C<EE<lt>numberE<gt>> | |
494 | ||
495 | The ASCII/Latin-1/Unicode character with that number. A | |
496 | leading "0x" means that I<number> is hex, as in | |
497 | C<EE<lt>0x201EE<gt>>. A leading "0" means that I<number> is octal, | |
498 | as in C<EE<lt>075E<gt>>. Otherwise I<number> is interpreted as being | |
499 | in decimal, as in C<EE<lt>181E<gt>>. | |
500 | ||
501 | Note that older Pod formatters might not recognize octal or | |
502 | hex numeric escapes, and that many formatters cannot reliably | |
503 | render characters above 255. (Some formatters may even have | |
504 | to use compromised renderings of Latin-1 characters, like | |
505 | rendering C<EE<lt>eacuteE<gt>> as just a plain "e".) | |
506 | ||
507 | =back | |
508 | ||
509 | =item C<FE<lt>filenameE<gt>> -- used for filenames | |
d74e8afc | 510 | X<F> X<< FZ<><> >> X<POD, formatting code, filename> X<filename> |
8a93676d SB |
511 | |
512 | Typically displayed in italics. Example: "C<FE<lt>.cshrcE<gt>>" | |
513 | ||
514 | =item C<SE<lt>textE<gt>> -- text contains non-breaking spaces | |
d74e8afc ITB |
515 | X<S> X<< SZ<><> >> X<POD, formatting code, non-breaking space> |
516 | X<non-breaking space> | |
8a93676d SB |
517 | |
518 | This means that the words in I<text> should not be broken | |
519 | across lines. Example: S<C<SE<lt>$x ? $y : $zE<gt>>>. | |
520 | ||
521 | =item C<XE<lt>topic nameE<gt>> -- an index entry | |
d74e8afc | 522 | X<X> X<< XZ<><> >> X<POD, formatting code, index entry> X<index entry> |
8a93676d SB |
523 | |
524 | This is ignored by most formatters, but some may use it for building | |
525 | indexes. It always renders as empty-string. | |
526 | Example: C<XE<lt>absolutizing relative URLsE<gt>> | |
527 | ||
528 | =item C<ZE<lt>E<gt>> -- a null (zero-effect) formatting code | |
d74e8afc | 529 | X<Z> X<< ZZ<><> >> X<POD, formatting code, null> X<null> |
8a93676d SB |
530 | |
531 | This is rarely used. It's one way to get around using an | |
532 | EE<lt>...E<gt> code sometimes. For example, instead of | |
533 | "C<NEE<lt>ltE<gt>3>" (for "NE<lt>3") you could write | |
534 | "C<NZE<lt>E<gt>E<lt>3>" (the "ZE<lt>E<gt>" breaks up the "N" and | |
535 | the "E<lt>" so they can't be considered | |
6c1c521a | 536 | the part of a (fictitious) "NE<lt>...E<gt>" code). |
8a93676d SB |
537 | |
538 | =for comment | |
539 | This was formerly explained as a "zero-width character". But it in | |
540 | most parser models, it parses to nothing at all, as opposed to parsing | |
541 | as if it were a E<zwnj> or E<zwj>, which are REAL zero-width characters. | |
542 | So "width" and "character" are exactly the wrong words. | |
543 | ||
544 | =back | |
545 | ||
546 | Most of the time, you will need only a single set of angle brackets to | |
547 | delimit the beginning and end of formatting codes. However, | |
548 | sometimes you will want to put a real right angle bracket (a | |
549 | greater-than sign, '>') inside of a formatting code. This is particularly | |
550 | common when using a formatting code to provide a different font-type for a | |
551 | snippet of code. As with all things in Perl, there is more than | |
552 | one way to do it. One way is to simply escape the closing bracket | |
553 | using an C<E> code: | |
5455df32 GS |
554 | |
555 | C<$a E<lt>=E<gt> $b> | |
556 | ||
557 | This will produce: "C<$a E<lt>=E<gt> $b>" | |
558 | ||
8a93676d | 559 | A more readable, and perhaps more "plain" way is to use an alternate |
8162142b JD |
560 | set of delimiters that doesn't require a single ">" to be escaped. |
561 | Doubled angle brackets ("<<" and ">>") may be used I<if and only if there is | |
8a93676d SB |
562 | whitespace right after the opening delimiter and whitespace right |
563 | before the closing delimiter!> For example, the following will | |
564 | do the trick: | |
d74e8afc | 565 | X<POD, formatting code, escaping with multiple brackets> |
5455df32 GS |
566 | |
567 | C<< $a <=> $b >> | |
568 | ||
569 | In fact, you can use as many repeated angle-brackets as you like so | |
570 | long as you have the same number of them in the opening and closing | |
571 | delimiters, and make sure that whitespace immediately follows the last | |
8a93676d SB |
572 | '<' of the opening delimiter, and immediately precedes the first '>' |
573 | of the closing delimiter. (The whitespace is ignored.) So the | |
574 | following will also work: | |
d74e8afc | 575 | X<POD, formatting code, escaping with multiple brackets> |
5455df32 GS |
576 | |
577 | C<<< $a <=> $b >>> | |
8a93676d | 578 | C<<<< $a <=> $b >>>> |
5455df32 | 579 | |
8a93676d SB |
580 | And they all mean exactly the same as this: |
581 | ||
582 | C<$a E<lt>=E<gt> $b> | |
583 | ||
a3d78747 RS |
584 | The multiple-bracket form does not affect the interpretation of the contents of |
585 | the formatting code, only how it must end. That means that the examples above | |
586 | are also exactly the same as this: | |
587 | ||
588 | C<< $a E<lt>=E<gt> $b >> | |
589 | ||
8a93676d SB |
590 | As a further example, this means that if you wanted to put these bits of |
591 | code in C<C> (code) style: | |
592 | ||
593 | open(X, ">>thing.dat") || die $! | |
594 | $foo->bar(); | |
595 | ||
596 | you could do it like so: | |
597 | ||
598 | C<<< open(X, ">>thing.dat") || die $! >>> | |
599 | C<< $foo->bar(); >> | |
5455df32 | 600 | |
8a93676d SB |
601 | which is presumably easier to read than the old way: |
602 | ||
603 | C<open(X, "E<gt>E<gt>thing.dat") || die $!> | |
c58e3c1c | 604 | C<$foo-E<gt>bar();> |
8a93676d SB |
605 | |
606 | This is currently supported by pod2text (Pod::Text), pod2man (Pod::Man), | |
607 | and any other pod2xxx or Pod::Xxxx translators that use | |
608 | Pod::Parser 1.093 or later, or Pod::Tree 1.02 or later. | |
5455df32 | 609 | |
b74bceb9 | 610 | =head2 The Intent |
d74e8afc | 611 | X<POD, intent of> |
3141265f | 612 | |
8a93676d SB |
613 | The intent is simplicity of use, not power of expression. Paragraphs |
614 | look like paragraphs (block format), so that they stand out | |
615 | visually, and so that I could run them through C<fmt> easily to reformat | |
616 | them (that's F7 in my version of B<vi>, or Esc Q in my version of | |
617 | B<emacs>). I wanted the translator to always leave the C<'> and C<`> and | |
618 | C<"> quotes alone, in verbatim mode, so I could slurp in a | |
619 | working program, shift it over four spaces, and have it print out, er, | |
620 | verbatim. And presumably in a monospace font. | |
621 | ||
622 | The Pod format is not necessarily sufficient for writing a book. Pod | |
623 | is just meant to be an idiot-proof common source for nroff, HTML, | |
624 | TeX, and other markup languages, as used for online | |
625 | documentation. Translators exist for B<pod2text>, B<pod2html>, | |
626 | B<pod2man> (that's for nroff(1) and troff(1)), B<pod2latex>, and | |
627 | B<pod2fm>. Various others are available in CPAN. | |
628 | ||
a0d0e21e | 629 | |
b74bceb9 | 630 | =head2 Embedding Pods in Perl Modules |
d74e8afc | 631 | X<POD, embedding> |
4633a7c4 | 632 | |
13d0d101 JK |
633 | You can embed Pod documentation in your Perl modules and scripts. Start |
634 | your documentation with an empty line, a "=head1" command at the | |
635 | beginning, and end it with a "=cut" command and an empty line. The | |
636 | B<perl> executable will ignore the Pod text. You can place a Pod | |
637 | statement where B<perl> expects the beginning of a new statement, but | |
638 | not within a statement, as that would result in an error. See any of | |
639 | the supplied library modules for examples. | |
640 | ||
641 | If you're going to put your Pod at the end of the file, and you're using | |
642 | an C<__END__> or C<__DATA__> cut mark, make sure to put an empty line there | |
643 | before the first Pod command. | |
cb1a09d0 | 644 | |
8a93676d | 645 | __END__ |
cb1a09d0 | 646 | |
8a93676d | 647 | =head1 NAME |
cb1a09d0 | 648 | |
8a93676d | 649 | Time::Local - efficiently compute time from local and GMT time |
cb1a09d0 | 650 | |
8a93676d SB |
651 | Without that empty line before the "=head1", many translators wouldn't |
652 | have recognized the "=head1" as starting a Pod block. | |
cb1a09d0 | 653 | |
8a93676d | 654 | =head2 Hints for Writing Pod |
1294c5d8 | 655 | |
8a93676d | 656 | =over |
1294c5d8 JM |
657 | |
658 | =item * | |
d74e8afc | 659 | X<podchecker> X<POD, validating> |
1294c5d8 | 660 | |
8a93676d SB |
661 | The B<podchecker> command is provided for checking Pod syntax for errors |
662 | and warnings. For example, it checks for completely blank lines in | |
663 | Pod blocks and for unknown commands and formatting codes. You should | |
664 | still also pass your document through one or more translators and proofread | |
665 | the result, or print out the result and proofread that. Some of the | |
666 | problems found may be bugs in the translators, which you may or may not | |
667 | wish to work around. | |
1294c5d8 JM |
668 | |
669 | =item * | |
670 | ||
8a93676d | 671 | If you're more familiar with writing in HTML than with writing in Pod, you |
210b36aa | 672 | can try your hand at writing documentation in simple HTML, and converting |
8a93676d SB |
673 | it to Pod with the experimental L<Pod::HTML2Pod|Pod::HTML2Pod> module, |
674 | (available in CPAN), and looking at the resulting code. The experimental | |
675 | L<Pod::PXML|Pod::PXML> module in CPAN might also be useful. | |
676 | ||
677 | =item * | |
678 | ||
679 | Many older Pod translators require the lines before every Pod | |
680 | command and after every Pod command (including "=cut"!) to be a blank | |
681 | line. Having something like this: | |
682 | ||
683 | # - - - - - - - - - - - - | |
684 | =item $firecracker->boom() | |
210b36aa | 685 | |
8a93676d SB |
686 | This noisily detonates the firecracker object. |
687 | =cut | |
688 | sub boom { | |
689 | ... | |
690 | ||
691 | ...will make such Pod translators completely fail to see the Pod block | |
692 | at all. | |
693 | ||
694 | Instead, have it like this: | |
695 | ||
696 | # - - - - - - - - - - - - | |
210b36aa | 697 | |
8a93676d | 698 | =item $firecracker->boom() |
210b36aa | 699 | |
8a93676d | 700 | This noisily detonates the firecracker object. |
210b36aa | 701 | |
8a93676d | 702 | =cut |
210b36aa | 703 | |
8a93676d SB |
704 | sub boom { |
705 | ... | |
706 | ||
707 | =item * | |
708 | ||
709 | Some older Pod translators require paragraphs (including command | |
710 | paragraphs like "=head2 Functions") to be separated by I<completely> | |
711 | empty lines. If you have an apparently empty line with some spaces | |
712 | on it, this might not count as a separator for those translators, and | |
713 | that could cause odd formatting. | |
714 | ||
715 | =item * | |
1294c5d8 | 716 | |
8a93676d SB |
717 | Older translators might add wording around an LE<lt>E<gt> link, so that |
718 | C<LE<lt>Foo::BarE<gt>> may become "the Foo::Bar manpage", for example. | |
719 | So you shouldn't write things like C<the LE<lt>fooE<gt> | |
ac036724 | 720 | documentation>, if you want the translated document to read sensibly. |
721 | Instead, write C<the LE<lt>Foo::Bar|Foo::BarE<gt> documentation> or | |
8a93676d SB |
722 | C<LE<lt>the Foo::Bar documentation|Foo::BarE<gt>>, to control how the |
723 | link comes out. | |
b74bceb9 | 724 | |
1294c5d8 JM |
725 | =item * |
726 | ||
8a93676d SB |
727 | Going past the 70th column in a verbatim block might be ungracefully |
728 | wrapped by some formatters. | |
1294c5d8 JM |
729 | |
730 | =back | |
731 | ||
cb1a09d0 AD |
732 | =head1 SEE ALSO |
733 | ||
8a93676d SB |
734 | L<perlpodspec>, L<perlsyn/"PODs: Embedded Documentation">, |
735 | L<perlnewmod>, L<perldoc>, L<pod2html>, L<pod2man>, L<podchecker>. | |
4633a7c4 | 736 | |
cb1a09d0 | 737 | =head1 AUTHOR |
a0d0e21e | 738 | |
8a93676d | 739 | Larry Wall, Sean M. Burke |
a0d0e21e | 740 | |
8a93676d | 741 | =cut |