3 perllocale - Perl locale handling (internationalization and localization)
7 Perl supports language-specific notions of data such as "is this a
8 letter", "what is the upper-case equivalent of this letter", and "which
9 of these letters comes first". These are important issues, especially
10 for languages other than English - but also for English: it would be
11 very naE<iuml>ve to think that C<A-Za-z> defines all the "letters". Perl
12 is also aware that some character other than '.' may be preferred as a
13 decimal point, and that output date representations may be
14 language-specific. The process of making an application take account of
15 its users' preferences in such matters is called B<internationalization>
16 (often abbreviated as B<i18n>); telling such an application about a
17 particular set of preferences is known as B<localization> (B<l10n>).
19 Perl can understand language-specific data via the standardized (ISO C,
20 XPG4, POSIX 1.c) method called "the locale system". The locale system is
21 controlled per application using one pragma, one function call, and
22 several environment variables.
24 B<NOTE>: This feature is new in Perl 5.004, and does not apply unless an
25 application specifically requests it - see L<Backward compatibility>.
27 =head1 PREPARING TO USE LOCALES
29 If Perl applications are to be able to understand and present your data
30 correctly according a locale of your choice, B<all> of the following
37 B<Your operating system must support the locale system>. If it does,
38 you should find that the setlocale() function is a documented part of
43 B<Definitions for the locales which you use must be installed>. You, or
44 your system administrator, must make sure that this is the case. The
45 available locales, the location in which they are kept, and the manner
46 in which they are installed, vary from system to system. Some systems
47 provide only a few, hard-wired, locales, and do not allow more to be
48 added; others allow you to add "canned" locales provided by the system
49 supplier; still others allow you or the system administrator to define
50 and add arbitrary locales. (You may have to ask your supplier to
51 provide canned locales which are not delivered with your operating
52 system.) Read your system documentation for further illumination.
56 B<Perl must believe that the locale system is supported>. If it does,
57 C<perl -V:d_setlocale> will say that the value for C<d_setlocale> is
62 If you want a Perl application to process and present your data
63 according to a particular locale, the application code should include
64 the S<C<use locale>> pragma (see L<The use locale Pragma>) where
65 appropriate, and B<at least one> of the following must be true:
71 B<The locale-determining environment variables (see L<"ENVIRONMENT">)
72 must be correctly set up>, either by yourself, or by the person who set
73 up your system account, at the time the application is started.
77 B<The application must set its own locale> using the method described in
78 L<The setlocale function>.
84 =head2 The use locale pragma
86 By default, Perl ignores the current locale. The S<C<use locale>>
87 pragma tells Perl to use the current locale for some operations:
93 B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) and
94 the POSIX string collation functions strcoll() and strxfrm() use
95 C<LC_COLLATE>. sort() is also affected if it is used without an
96 explicit comparison function because it uses C<cmp> by default.
98 B<Note:> C<eq> and C<ne> are unaffected by the locale: they always
99 perform a byte-by-byte comparison of their scalar operands. What's
100 more, if C<cmp> finds that its operands are equal according to the
101 collation sequence specified by the current locale, it goes on to
102 perform a byte-by-byte comparison, and only returns I<0> (equal) if the
103 operands are bit-for-bit identical. If you really want to know whether
104 two strings - which C<eq> and C<cmp> may consider different - are equal
105 as far as collation in the locale is concerned, see the discussion in
106 L<Category LC_COLLATE: Collation>.
110 B<Regular expressions and case-modification functions> (uc(), lc(),
111 ucfirst(), and lcfirst()) use C<LC_CTYPE>
115 B<The formatting functions> (printf(), sprintf() and write()) use
120 B<The POSIX date formatting function> (strftime()) uses C<LC_TIME>.
124 C<LC_COLLATE>, C<LC_CTYPE>, and so on, are discussed further in L<LOCALE
127 The default behavior returns with S<C<no locale>> or on reaching the
128 end of the enclosing block.
130 Note that the string result of any operation that uses locale
131 information is tainted, as it is possible for a locale to be
132 untrustworthy. See L<"SECURITY">.
134 =head2 The setlocale function
136 You can switch locales as often as you wish at run time with the
137 POSIX::setlocale() function:
139 # This functionality not usable prior to Perl 5.004
142 # Import locale-handling tool set from POSIX module.
143 # This example uses: setlocale -- the function call
144 # LC_CTYPE -- explained below
145 use POSIX qw(locale_h);
147 # query and save the old locale
148 $old_locale = setlocale(LC_CTYPE);
150 setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
151 # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
153 setlocale(LC_CTYPE, "");
154 # LC_CTYPE now reset to default defined by LC_ALL/LC_CTYPE/LANG
155 # environment variables. See below for documentation.
157 # restore the old locale
158 setlocale(LC_CTYPE, $old_locale);
160 The first argument of setlocale() gives the B<category>, the second the
161 B<locale>. The category tells in what aspect of data processing you
162 want to apply locale-specific rules. Category names are discussed in
163 L<LOCALE CATEGORIES> and L<"ENVIRONMENT">. The locale is the name of a
164 collection of customization information corresponding to a particular
165 combination of language, country or territory, and codeset. Read on for
166 hints on the naming of locales: not all systems name locales as in the
169 If no second argument is provided, the function returns a string naming
170 the current locale for the category. You can use this value as the
171 second argument in a subsequent call to setlocale(). If a second
172 argument is given and it corresponds to a valid locale, the locale for
173 the category is set to that value, and the function returns the
174 now-current locale value. You can use this in a subsequent call to
175 setlocale(). (In some implementations, the return value may sometimes
176 differ from the value you gave as the second argument - think of it as
177 an alias for the value that you gave.)
179 As the example shows, if the second argument is an empty string, the
180 category's locale is returned to the default specified by the
181 corresponding environment variables. Generally, this results in a
182 return to the default which was in force when Perl started up: changes
183 to the environment made by the application after start-up may or may not
184 be noticed, depending on the implementation of your system's C library.
186 If the second argument does not correspond to a valid locale, the locale
187 for the category is not changed, and the function returns I<undef>.
189 For further information about the categories, consult L<setlocale(3)>.
190 For the locales available in your system, also consult L<setlocale(3)>
191 and see whether it leads you to the list of the available locales
192 (search for the I<SEE ALSO> section). If that fails, try the following
205 and see whether they list something resembling these
207 en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
210 english german russian
211 english.iso88591 german.iso88591 russian.iso88595
213 Sadly, even though the calling interface for setlocale() has been
214 standardized, the names of the locales and the directories where
215 the configuration is, have not. The basic form of the name is
216 I<language_country/territory>B<.>I<codeset>, but the
217 latter parts are not always present.
219 Two special locales are worth particular mention: "C" and "POSIX".
220 Currently these are effectively the same locale: the difference is
221 mainly that the first one is defined by the C standard and the second by
222 the POSIX standard. What they define is the B<default locale> in which
223 every program starts in the absence of locale information in its
224 environment. (The default default locale, if you will.) Its language
225 is (American) English and its character codeset ASCII.
227 B<NOTE>: Not all systems have the "POSIX" locale (not all systems are
228 POSIX-conformant), so use "C" when you need explicitly to specify this
231 =head2 The localeconv function
233 The POSIX::localeconv() function allows you to get particulars of the
234 locale-dependent numeric formatting information specified by the current
235 C<LC_NUMERIC> and C<LC_MONETARY> locales. (If you just want the name of
236 the current locale for a particular category, use POSIX::setlocale()
237 with a single parameter - see L<The setlocale function>.)
239 use POSIX qw(locale_h);
241 # Get a reference to a hash of locale-dependent info
242 $locale_values = localeconv();
244 # Output sorted list of the values
245 for (sort keys %$locale_values) {
246 printf "%-20s = %s\n", $_, $locale_values->{$_}
249 localeconv() takes no arguments, and returns B<a reference to> a hash.
250 The keys of this hash are formatting variable names such as
251 C<decimal_point> and C<thousands_sep>; the values are the corresponding
252 values. See L<POSIX (3)/localeconv> for a longer example, which lists
253 all the categories an implementation might be expected to provide; some
254 provide more and others fewer, however. Note that you don't need C<use
255 locale>: as a function with the job of querying the locale, localeconv()
256 always observes the current locale.
258 Here's a simple-minded example program which rewrites its command line
259 parameters as integers formatted correctly in the current locale:
261 # See comments in previous example
263 use POSIX qw(locale_h);
265 # Get some of locale's numeric formatting parameters
266 my ($thousands_sep, $grouping) =
267 @{localeconv()}{'thousands_sep', 'grouping'};
269 # Apply defaults if values are missing
270 $thousands_sep = ',' unless $thousands_sep;
271 $grouping = 3 unless $grouping;
273 # Format command line params for current locale
275 $_ = int; # Chop non-integer part
277 s/(\d)(\d{$grouping}($|$thousands_sep))/$1$thousands_sep$2/;
282 =head1 LOCALE CATEGORIES
284 The subsections which follow describe basic locale categories. As well
285 as these, there are some combination categories which allow the
286 manipulation of more than one basic category at a time. See
287 L<"ENVIRONMENT"> for a discussion of these.
289 =head2 Category LC_COLLATE: Collation
291 When in the scope of S<C<use locale>>, Perl looks to the C<LC_COLLATE>
292 environment variable to determine the application's notions on the
293 collation (ordering) of characters. ('b' follows 'a' in Latin
294 alphabets, but where do 'E<aacute>' and 'E<aring>' belong?)
296 Here is a code snippet that will tell you what are the alphanumeric
297 characters in the current locale, in the locale order:
300 print +(sort grep /\w/, map { chr() } 0..255), "\n";
302 Compare this with the characters that you see and their order if you
303 state explicitly that the locale should be ignored:
306 print +(sort grep /\w/, map { chr() } 0..255), "\n";
308 This machine-native collation (which is what you get unless S<C<use
309 locale>> has appeared earlier in the same block) must be used for
310 sorting raw binary data, whereas the locale-dependent collation of the
311 first example is useful for natural text.
313 As noted in L<USING LOCALES>, C<cmp> compares according to the current
314 collation locale when C<use locale> is in effect, but falls back to a
315 byte-by-byte comparison for strings which the locale says are equal. You
316 can use POSIX::strcoll() if you don't want this fall-back:
318 use POSIX qw(strcoll);
320 !strcoll("space and case ignored", "SpaceAndCaseIgnored");
322 $equal_in_locale will be true if the collation locale specifies a
323 dictionary-like ordering which ignores space characters completely, and
324 which folds case. Alternatively, you can use this idiom:
327 $s_a = "space and case ignored";
328 $s_b = "SpaceAndCaseIgnored";
329 $equal_in_locale = $s_a ge $s_b && $s_a le $s_b;
331 which works because neither C<ne> nor C<ge> falls back to doing a
332 byte-by-byte comparison when the operands are equal according to the
333 locale. The idiom may be less efficient than using strcoll(), but,
334 unlike that function, it is not confused by strings containing embedded
337 If you have a single string which you want to check for "equality in
338 locale" against several others, you might think you could gain a little
339 efficiency by using POSIX::strxfrm() in conjunction with C<eq>:
341 use POSIX qw(strxfrm);
342 $xfrm_string = strxfrm("Mixed-case string");
343 print "locale collation ignores spaces\n"
344 if $xfrm_string eq strxfrm("Mixed-casestring");
345 print "locale collation ignores hyphens\n"
346 if $xfrm_string eq strxfrm("Mixedcase string");
347 print "locale collation ignores case\n"
348 if $xfrm_string eq strxfrm("mixed-case string");
350 strxfrm() takes a string and maps it into a transformed string for use
351 in byte-by-byte comparisons against other transformed strings during
352 collation. "Under the hood", locale-affected Perl comparison operators
353 call strxfrm() for both their operands, then do a byte-by-byte
354 comparison of the transformed strings. By calling strxfrm() explicitly,
355 and using a non locale-affected comparison, the example attempts to save
356 a couple of transformations. In fact, it doesn't save anything: Perl
357 magic (see L<perlguts/Magic>) creates the transformed version of a
358 string the first time it's needed in a comparison, then keeps it around
359 in case it's needed again. An example rewritten the easy way with
360 C<cmp> runs just about as fast. It also copes with null characters
361 embedded in strings; if you call strxfrm() directly, it treats the first
362 null it finds as a terminator. In short, don't call strxfrm() directly:
363 let Perl do it for you.
365 Note: C<use locale> isn't shown in some of these examples, as it isn't
366 needed: strcoll() and strxfrm() exist only to generate locale-dependent
367 results, and so always obey the current C<LC_COLLATE> locale.
369 =head2 Category LC_CTYPE: Character Types
371 When in the scope of S<C<use locale>>, Perl obeys the C<LC_CTYPE> locale
372 setting. This controls the application's notion of which characters are
373 alphabetic. This affects Perl's C<\w> regular expression metanotation,
374 which stands for alphanumeric characters - that is, alphabetic and
375 numeric characters. (Consult L<perlre> for more information about
376 regular expressions.) Thanks to C<LC_CTYPE>, depending on your locale
377 setting, characters like 'E<aelig>', 'E<eth>', 'E<szlig>', and
378 'E<oslash>' may be understood as C<\w> characters.
380 C<LC_CTYPE> also affects the POSIX character-class test functions -
381 isalpha(), islower() and so on. For example, if you move from the "C"
382 locale to a 7-bit Scandinavian one, you may find - possibly to your
383 surprise - that "|" moves from the ispunct() class to isalpha().
385 B<Note:> A broken or malicious C<LC_CTYPE> locale definition may result
386 in clearly ineligible characters being considered to be alphanumeric by
387 your application. For strict matching of (unaccented) letters and
388 digits - for example, in command strings - locale-aware applications
389 should use C<\w> inside a C<no locale> block. See L<"SECURITY">.
391 =head2 Category LC_NUMERIC: Numeric Formatting
393 When in the scope of S<C<use locale>>, Perl obeys the C<LC_NUMERIC>
394 locale information, which controls application's idea of how numbers
395 should be formatted for human readability by the printf(), sprintf(),
396 and write() functions. String to numeric conversion by the
397 POSIX::strtod() function is also affected. In most implementations the
398 only effect is to change the character used for the decimal point -
399 perhaps from '.' to ',': these functions aren't aware of such niceties
400 as thousands separation and so on. (See L<The localeconv function> if
401 you care about these things.)
403 Note that output produced by print() is B<never> affected by the
404 current locale: it is independent of whether C<use locale> or C<no
405 locale> is in effect, and corresponds to what you'd get from printf()
406 in the "C" locale. The same is true for Perl's internal conversions
407 between numeric and string formats:
409 use POSIX qw(strtod);
412 $n = 5/2; # Assign numeric 2.5 to $n
414 $a = " $n"; # Locale-independent conversion to string
416 print "half five is $n\n"; # Locale-independent output
418 printf "half five is %g\n", $n; # Locale-dependent output
420 print "DECIMAL POINT IS COMMA\n"
421 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
423 =head2 Category LC_MONETARY: Formatting of monetary amounts
425 The C standard defines the C<LC_MONETARY> category, but no function that
426 is affected by its contents. (Those with experience of standards
427 committees will recognize that the working group decided to punt on the
428 issue.) Consequently, Perl takes no notice of it. If you really want
429 to use C<LC_MONETARY>, you can query its contents - see L<The localeconv
430 function> - and use the information that it returns in your
431 application's own formatting of currency amounts. However, you may well
432 find that the information, though voluminous and complex, does not quite
433 meet your requirements: currency formatting is a hard nut to crack.
437 The output produced by POSIX::strftime(), which builds a formatted
438 human-readable date/time string, is affected by the current C<LC_TIME>
439 locale. Thus, in a French locale, the output produced by the C<%B>
440 format element (full month name) for the first month of the year would
441 be "janvier". Here's how to get a list of the long month names in the
444 use POSIX qw(strftime);
446 $long_month_name[$_] =
447 strftime("%B", 0, 0, 0, 1, $_, 96);
450 Note: C<use locale> isn't needed in this example: as a function which
451 exists only to generate locale-dependent results, strftime() always
452 obeys the current C<LC_TIME> locale.
454 =head2 Other categories
456 The remaining locale category, C<LC_MESSAGES> (possibly supplemented by
457 others in particular implementations) is not currently used by Perl -
458 except possibly to affect the behavior of library functions called by
459 extensions which are not part of the standard Perl distribution.
463 While the main discussion of Perl security issues can be found in
464 L<perlsec>, a discussion of Perl's locale handling would be incomplete
465 if it did not draw your attention to locale-dependent security issues.
466 Locales - particularly on systems which allow unprivileged users to
467 build their own locales - are untrustworthy. A malicious (or just plain
468 broken) locale can make a locale-aware application give unexpected
469 results. Here are a few possibilities:
475 Regular expression checks for safe file names or mail addresses using
476 C<\w> may be spoofed by an C<LC_CTYPE> locale which claims that
477 characters such as "E<gt>" and "|" are alphanumeric.
481 If the decimal point character in the C<LC_NUMERIC> locale is
482 surreptitiously changed from a dot to a comma, C<sprintf("%g",
483 0.123456e3)> produces a string result of "123,456". Many people would
484 interpret this as one hundred and twenty-three thousand, four hundred
489 A sneaky C<LC_COLLATE> locale could result in the names of students with
490 "D" grades appearing ahead of those with "A"s.
494 An application which takes the trouble to use the information in
495 C<LC_MONETARY> may format debits as if they were credits and vice versa
496 if that locale has been subverted. Or it make may make payments in US
497 dollars instead of Hong Kong dollars.
501 The date and day names in dates formatted by strftime() could be
502 manipulated to advantage by a malicious user able to subvert the
503 C<LC_DATE> locale. ("Look - it says I wasn't in the building on
508 Such dangers are not peculiar to the locale system: any aspect of an
509 application's environment which may maliciously be modified presents
510 similar challenges. Similarly, they are not specific to Perl: any
511 programming language which allows you to write programs which take
512 account of their environment exposes you to these issues.
514 Perl cannot protect you from all of the possibilities shown in the
515 examples - there is no substitute for your own vigilance - but, when
516 C<use locale> is in effect, Perl uses the tainting mechanism (see
517 L<perlsec>) to mark string results which become locale-dependent, and
518 which may be untrustworthy in consequence. Here is a summary of the
519 tainting behavior of operators and functions which may be affected by
524 =item B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>):
526 Scalar true/false (or less/equal/greater) result is never tainted.
528 =item B<Matching operator> (C<m//>):
530 Scalar true/false result never tainted.
532 Subpatterns, either delivered as an array-context result, or as $1 etc.
533 are tainted if C<use locale> is in effect, and the subpattern regular
534 expression contains C<\w> (to match an alphanumeric character). The
535 matched pattern variable, $&, is also tainted if C<use locale> is in
536 effect, and the regular expression contains C<\w>.
538 =item B<Substitution operator> (C<s///>):
540 Has the same behavior as the match operator. When C<use locale> is
541 in effect, he left operand of C<=~> will become tainted if it is
542 modified as a result of a substitution based on a regular expression
543 match involving C<\w>.
545 =item B<In-memory formatting function> (sprintf()):
547 Result is tainted if "use locale" is in effect.
549 =item B<Output formatting functions> (printf() and write()):
551 Success/failure result is never tainted.
553 =item B<Case-mapping functions> (lc(), lcfirst(), uc(), ucfirst()):
555 Results are tainted if C<use locale> is in effect.
557 =item B<POSIX locale-dependent functions> (localeconv(), strcoll(),
558 strftime(), strxfrm()):
560 Results are never tainted.
562 =item B<POSIX character class tests> (isalnum(), isalpha(), isdigit(),
563 isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(),
566 True/false results are never tainted.
570 Three examples illustrate locale-dependent tainting.
571 The first program, which ignores its locale, won't run: a value taken
572 directly from the command-line may not be used to name an output file
573 when taint checks are enabled.
575 #/usr/local/bin/perl -T
576 # Run with taint checking
578 # Command-line sanity check omitted...
579 $tainted_output_file = shift;
581 open(F, ">$tainted_output_file")
582 or warn "Open of $untainted_output_file failed: $!\n";
584 The program can be made to run by "laundering" the tainted value through
585 a regular expression: the second example - which still ignores locale
586 information - runs, creating the file named on its command-line
589 #/usr/local/bin/perl -T
591 $tainted_output_file = shift;
592 $tainted_output_file =~ m%[\w/]+%;
593 $untainted_output_file = $&;
595 open(F, ">$untainted_output_file")
596 or warn "Open of $untainted_output_file failed: $!\n";
598 Compare this with a very similar program which is locale-aware:
600 #/usr/local/bin/perl -T
602 $tainted_output_file = shift;
604 $tainted_output_file =~ m%[\w/]+%;
605 $localized_output_file = $&;
607 open(F, ">$localized_output_file")
608 or warn "Open of $localized_output_file failed: $!\n";
610 This third program fails to run because $& is tainted: it is the result
611 of a match involving C<\w> when C<use locale> is in effect.
619 A string that can suppress Perl's warning about failed locale settings
620 at start-up. Failure can occur if the locale support in the operating
621 system is lacking (broken) is some way - or if you mistyped the name of
622 a locale when you set up your environment. If this environment variable
623 is absent, or has a value which does not evaluate to integer zero - that
624 is "0" or "" - Perl will complain about locale setting failures.
626 B<NOTE>: PERL_BADLANG only gives you a way to hide the warning message.
627 The message tells about some problem in your system's locale support,
628 and you should investigate what the problem is.
632 The following environment variables are not specific to Perl: They are
633 part of the standardized (ISO C, XPG4, POSIX 1.c) setlocale() method
634 for controlling an application's opinion on data.
640 C<LC_ALL> is the "override-all" locale environment variable. If it is
641 set, it overrides all the rest of the locale environment variables.
645 In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type
646 locale. In the absence of both C<LC_ALL> and C<LC_CTYPE>, C<LANG>
647 chooses the character type locale.
651 In the absence of C<LC_ALL>, C<LC_COLLATE> chooses the collation
652 (sorting) locale. In the absence of both C<LC_ALL> and C<LC_COLLATE>,
653 C<LANG> chooses the collation locale.
657 In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the monetary
658 formatting locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>,
659 C<LANG> chooses the monetary formatting locale.
663 In the absence of C<LC_ALL>, C<LC_NUMERIC> chooses the numeric format
664 locale. In the absence of both C<LC_ALL> and C<LC_NUMERIC>, C<LANG>
665 chooses the numeric format.
669 In the absence of C<LC_ALL>, C<LC_TIME> chooses the date and time
670 formatting locale. In the absence of both C<LC_ALL> and C<LC_TIME>,
671 C<LANG> chooses the date and time formatting locale.
675 C<LANG> is the "catch-all" locale environment variable. If it is set, it
676 is used as the last resort after the overall C<LC_ALL> and the
677 category-specific C<LC_...>.
683 =head2 Backward compatibility
685 Versions of Perl prior to 5.004 B<mostly> ignored locale information,
686 generally behaving as if something similar to the C<"C"> locale (see
687 L<The setlocale function>) was always in force, even if the program
688 environment suggested otherwise. By default, Perl still behaves this
689 way so as to maintain backward compatibility. If you want a Perl
690 application to pay attention to locale information, you B<must> use
691 the S<C<use locale>> pragma (see L<The S<C<use locale>> Pragma>) to
692 instruct it to do so.
694 Versions of Perl from 5.002 to 5.003 did use the C<LC_CTYPE>
695 information if that was available, that is, C<\w> did understand what
696 are the letters according to the locale environment variables.
697 The problem was that the user had no control over the feature:
698 if the C library supported locales, Perl used them.
700 =head2 I18N:Collate obsolete
702 In versions of Perl prior to 5.004 per-locale collation was possible
703 using the C<I18N::Collate> library module. This module is now mildly
704 obsolete and should be avoided in new applications. The C<LC_COLLATE>
705 functionality is now integrated into the Perl core language: One can
706 use locale-specific scalar data completely normally with C<use locale>,
707 so there is no longer any need to juggle with the scalar references of
710 =head2 Sort speed and memory use impacts
712 Comparing and sorting by locale is usually slower than the default
713 sorting; slow-downs of two to four times have been observed. It will
714 also consume more memory: once a Perl scalar variable has participated
715 in any string comparison or sorting operation obeying the locale
716 collation rules, it will take 3-15 times more memory than before. (The
717 exact multiplier depends on the string's contents, the operating system
718 and the locale.) These downsides are dictated more by the operating
719 system's implementation of the locale system than by Perl.
721 =head2 Freely available locale definitions
723 There is a large collection of locale definitions at
724 C<ftp://dkuug.dk/i18n/WG15-collection>. You should be aware that it is
725 unsupported, and is not claimed to be fit for any purpose. If your
726 system allows the installation of arbitrary locales, you may find the
727 definitions useful as they are, or as a basis for the development of
732 "Internationalization" is often abbreviated as B<i18n> because its first
733 and last letters are separated by eighteen others. (You may guess why
734 the internalin ... internaliti ... i18n tends to get abbreviated.) In
735 the same way, "localization" is often abbreviated to B<l10n>.
737 =head2 An imperfect standard
739 Internationalization, as defined in the C and POSIX standards, can be
740 criticized as incomplete, ungainly, and having too large a granularity.
741 (Locales apply to a whole process, when it would arguably be more useful
742 to have them apply to a single thread, window group, or whatever.) They
743 also have a tendency, like standards groups, to divide the world into
744 nations, when we all know that the world can equally well be divided
745 into bankers, bikers, gamers, and so on. But, for now, it's the only
746 standard we've got. This may be construed as a bug.
750 =head2 Broken systems
752 In certain system environments the operating system's locale support
753 is broken and cannot be fixed or used by Perl. Such deficiencies can
754 and will result in mysterious hangs and/or Perl core dumps when the
755 C<use locale> is in effect. When confronted with such a system,
756 please report in excruciating detail to C<perlbug@perl.com>, and
757 complain to your vendor: maybe some bug fixes exist for these problems
758 in your operating system. Sometimes such bug fixes are called an
759 operating system upgrade.
763 L<POSIX (3)/isalnum>, L<POSIX (3)/isalpha>, L<POSIX (3)/isdigit>,
764 L<POSIX (3)/isgraph>, L<POSIX (3)/islower>, L<POSIX (3)/isprint>,
765 L<POSIX (3)/ispunct>, L<POSIX (3)/isspace>, L<POSIX (3)/isupper>,
766 L<POSIX (3)/isxdigit>, L<POSIX (3)/localeconv>, L<POSIX (3)/setlocale>,
767 L<POSIX (3)/strcoll>, L<POSIX (3)/strftime>, L<POSIX (3)/strtod>,
772 Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
773 Dunlop, assisted by the perl5-porters.
775 Last update: Tue Dec 24 16:43:11 EST 1996