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Locale::Maketext(Perl Programmers Reference GLocale::Maketext(3p)

       Locale::Maketext - framework for localization

         package MyProgram;
         use strict;
         use MyProgram::L10N;
          # ...which inherits from Locale::Maketext
         my $lh = MyProgram::L10N->get_handle() || die "What language?";
         # And then any messages your program emits, like:
         warn $lh->maketext( "Can't open file [_1]: [_2]\n", $f, $! );

       It is a common feature of applications (whether run
       directly, or via the Web) for them to be "localized" --
       i.e., for them to a present an English interface to an
       English-speaker, a German interface to a German-speaker,
       and so on for all languages it's programmed with.
       Locale::Maketext is a framework for software localization;
       it provides you with the tools for organizing and access-
       ing the bits of text and text-processing code that you
       need for producing localized applications.

       In order to make sense of Maketext and how all its compo-
       nents fit together, you should probably go read
       Locale::Maketext::TPJ13, and then read the following docu-

       You may also want to read over the source for "File::Find-
       grep" and its constituent modules -- they are a complete
       (if small) example application that uses Maketext.

       The basic design of Locale::Maketext is object-oriented,
       and Locale::Maketext is an abstract base class, from which
       you derive a "project class".  The project class (with a
       name like "TkBocciBall::Localize", which you then use in
       your module) is in turn the base class for all the "lan-
       guage classes" for your project (with names "TkBoc-
       ciBall::Localize::it", "TkBocciBall::Localize::en",
       "TkBocciBall::Localize::fr", etc.).

       A language class is a class containing a lexicon of
       phrases as class data, and possibly also some methods that
       are of use in interpreting phrases in the lexicon, or oth-
       erwise dealing with text in that language.

       An object belonging to a language class is called a "lan-
       guage handle"; it's typically a flyweight object.

       The normal course of action is to call:

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         use TkBocciBall::Localize;  # the localization project class
         $lh = TkBocciBall::Localize->get_handle();
          # Depending on the user's locale, etc., this will
          # make a language handle from among the classes available,
          # and any defaults that you declare.
         die "Couldn't make a language handle??" unless $lh;

       From then on, you use the "maketext" function to access
       entries in whatever lexicon(s) belong to the language han-
       dle you got.  So, this:

         print $lh->maketext("You won!"), "\n";

       ...emits the right text for this language.  If the object
       in $lh belongs to class "TkBocciBall::Localize::fr" and
       %TkBocciBall::Localize::fr::Lexicon contains "("You won!"
       => "Tu as gagne!")", then the above code happily tells the
       user "Tu as gagne!".

       Locale::Maketext offers a variety of methods, which fall
       into three categories:

       o   Methods to do with constructing language handles.

       o   "maketext" and other methods to do with accessing
           %Lexicon data for a given language handle.

       o   Methods that you may find it handy to use, from rou-
           tines of yours that you put in %Lexicon entries.

       These are covered in the following section.

       Construction Methods

       These are to do with constructing a language handle:

       o   $lh = YourProjClass->get_handle( ...langtags... ) ||
           die "lg-handle?";

           This tries loading classes based on the language-tags
           you give (like "("en-US", "sk", "kon", "es-MX", "ja",
           "i-klingon")", and for the first class that succeeds,
           returns YourProjClass::language->new().

           It runs thru the entire given list of language-tags,
           and finds no classes for those exact terms, it then
           tries "superordinate" language classes.  So if no
           "en-US" class (i.e., YourProjClass::en_us) was found,
           nor classes for anything else in that list, we then
           try its superordinate, "en" (i.e., YourProjClass::en),
           and so on thru the other language-tags in the given
           list: "es".  (The other language-tags in our example
           list: happen to have no superordinates.)

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           If none of those language-tags leads to loadable
           classes, we then try classes derived from YourProj-
           Class->fallback_languages() and then if nothing comes
           of that, we use classes named by YourProjClass->fall-
           back_language_classes().  Then in the (probably quite
           unlikely) event that that fails, we just return undef.

       o   $lh = YourProjClass->get_handle() || die "lg-handle?";

           When "get_handle" is called with an empty parameter
           list, magic happens:

           If "get_handle" senses that it's running in program
           that was invoked as a CGI, then it tries to get lan-
           guage-tags out of the environment variable
           "HTTP_ACCEPT_LANGUAGE", and it pretends that those
           were the languages passed as parameters to "get_han-

           Otherwise (i.e., if not a CGI), this tries various OS-
           specific ways to get the language-tags for the current
           locale/language, and then pretends that those were the
           value(s) passed to "get_handle".

           Currently this OS-specific stuff consists of looking
           in the environment variables "LANG" and "LANGUAGE";
           and on MSWin machines (where those variables are typi-
           cally unused), this also tries using the module
           Win32::Locale to get a language-tag for whatever lan-
           guage/locale is currently selected in the "Regional
           Settings" (or "International"?)  Control Panel.  I
           welcome further suggestions for making this do the
           Right Thing under other operating systems that support

           If you're using localization in an application that
           keeps a configuration file, you might consider some-
           thing like this in your project class:

             sub get_handle_via_config {
               my $class = $_[0];
               my $preferred_language = $Config_settings{'language'};
               my $lh;
               if($preferred_language) {
                 $lh = $class->get_handle($chosen_language)
                  || die "No language handle for \"$chosen_language\" or the like";
               } else {
                 # Config file missing, maybe?
                 $lh = $class->get_handle()
                  || die "Can't get a language handle";
               return $lh;

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       o   $lh = YourProjClass::langname->new();

           This constructs a language handle.  You usually don't
           call this directly, but instead let "get_handle" find
           a language class to "use" and to then call ->new on.

       o   $lh->init();

           This is called by ->new to initialize newly-con-
           structed language handles.  If you define an init
           method in your class, remember that it's usually con-
           sidered a good idea to call $lh->SUPER::init in it
           (presumably at the beginning), so that all classes get
           a chance to initialize a new object however they see

       o   YourProjClass->fallback_languages()

           "get_handle" appends the return value of this to the
           end of whatever list of languages you pass "get_han-
           dle".  Unless you override this method, your project
           class will inherit Locale::Maketext's "fallback_lan-
           guages", which currently returns "('i-default', 'en',
           'en-US')".  ("i-default" is defined in RFC 2277).

           This method (by having it return the name of a lan-
           guage-tag that has an existing language class) can be
           used for making sure that "get_handle" will always
           manage to construct a language handle (assuming your
           language classes are in an appropriate @INC direc-
           tory).  Or you can use the next method:

       o   YourProjClass->fallback_language_classes()

           "get_handle" appends the return value of this to the
           end of the list of classes it will try using.  Unless
           you override this method, your project class will
           inherit Locale::Maketext's "fallback_lan-
           guage_classes", which currently returns an empty list,
           "()".  By setting this to some value (namely, the name
           of a loadable language class), you can be sure that
           "get_handle" will always manage to construct a lan-
           guage handle.

       The "maketext" Method

       This is the most important method in Locale::Maketext:

       $text = $lh->maketext(key, ...parameters for this

       This looks in the %Lexicon of the language handle $lh and
       all its superclasses, looking for an entry whose key is
       the string key.  Assuming such an entry is found, various

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       things then happen, depending on the value found:

       If the value is a scalarref, the scalar is dereferenced
       and returned (and any parameters are ignored).  If the
       value is a coderef, we return &$value($lh, ...parame-
       ters...).  If the value is a string that doesn't look like
       it's in Bracket Notation, we return it (after replacing it
       with a scalarref, in its %Lexicon).  If the value does
       look like it's in Bracket Notation, then we compile it
       into a sub, replace the string in the %Lexicon with the
       new coderef, and then we return &$new_sub($lh, ...parame-

       Bracket Notation is discussed in a later section.  Note
       that trying to compile a string into Bracket Notation can
       throw an exception if the string is not syntactically
       valid (say, by not balancing brackets right.)

       Also, calling &$coderef($lh, ...parameters...) can throw
       any sort of exception (if, say, code in that sub tries to
       divide by zero).  But a very common exception occurs when
       you have Bracket Notation text that says to call a method
       "foo", but there is no such method.  (E.g., "You have
       [quatn,_1,ball]." will throw an exception on trying to
       call $lh->quatn($_[1],'ball') -- you presumably meant
       "quant".)  "maketext" catches these exceptions, but only
       to make the error message more readable, at which point it
       rethrows the exception.

       An exception may be thrown if key is not found in any of
       $lh's %Lexicon hashes.  What happens if a key is not
       found, is discussed in a later section, "Controlling
       Lookup Failure".

       Note that you might find it useful in some cases to over-
       ride the "maketext" method with an "after method", if you
       want to translate encodings, or even scripts:

           package YrProj::zh_cn; # Chinese with PRC-style glyphs
           use base ('YrProj::zh_tw');  # Taiwan-style
           sub maketext {
             my $self = shift(@_);
             my $value = $self->maketext(@_);
             return Chineeze::taiwan2mainland($value);

       Or you may want to override it with something that traps
       any exceptions, if that's critical to your program:

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         sub maketext {
           my($lh, @stuff) = @_;
           my $out;
           eval { $out = $lh->SUPER::maketext(@stuff) };
           return $out unless $@;
           ...otherwise deal with the exception...

       Other than those two situations, I don't imagine that it's
       useful to override the "maketext" method.  (If you run
       into a situation where it is useful, I'd be interested in
       hearing about it.)

       $lh->fail_with or $lh->fail_with(PARAM)
           These two methods are discussed in the section "Con-
           trolling Lookup Failure".

       Utility Methods

       These are methods that you may find it handy to use, gen-
       erally from %Lexicon routines of yours (whether expressed
       as Bracket Notation or not).

       $language->quant($number, $singular)
       $language->quant($number, $singular, $plural)
       $language->quant($number, $singular, $plural, $negative)
           This is generally meant to be called from inside
           Bracket Notation (which is discussed later), as in

                "Your search matched [quant,_1,document]!"

           It's for quantifying a noun (i.e., saying how much of
           it there is, while giving the correct form of it).
           The behavior of this method is handy for English and a
           few other Western European languages, and you should
           override it for languages where it's not suitable.
           You can feel free to read the source, but the current
           implementation is basically as this pseudocode

                if $number is 0 and there's a $negative,
                   return $negative;
                elsif $number is 1,
                   return "1 $singular";
                elsif there's a $plural,
                   return "$number $plural";
                   return "$number " . $singular . "s";
                # ...except that we actually call numf to
                #  stringify $number before returning it.

           So for English (with Bracket Notation)

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           "...[quant,_1,file]..." is fine (for 0 it returns "0
           files", for 1 it returns "1 file", and for more it
           returns "2 files", etc.)

           But for "directory", you'd want "[quant,_1,direc-
           tory,directories]" so that our elementary "quant"
           method doesn't think that the plural of "directory" is
           "directorys".  And you might find that the output may
           sound better if you specify a negative form, as in:

                "[quant,_1,file,files,No files] matched your query.\n"

           Remember to keep in mind verb agreement (or adjectives
           too, in other languages), as in:

                "[quant,_1,document] were matched.\n"

           Because if _1 is one, you get "1 document were
           matched".  An acceptable hack here is to do something
           like this:

                "[quant,_1,document was, documents were] matched.\n"

           This returns the given number formatted nicely accord-
           ing to this language's conventions.  Maketext's
           default method is mostly to just take the normal
           string form of the number (applying sprintf "%G" for
           only very large numbers), and then to add commas as
           necessary.  (Except that we apply "tr/,./.,/" if $lan-
           guage->{'numf_comma'} is true; that's a bit of a hack
           that's useful for languages that express two million
           as "2.000.000" and not as "2,000,000").

           If you want anything fancier, consider overriding this
           with something that uses Number::Format, or does some-
           thing else entirely.

           Note that numf is called by quant for stringifying all
           quantifying numbers.

       $language->sprintf($format, @items)
           This is just a wrapper around Perl's normal "sprintf"
           function.  It's provided so that you can use "sprintf"
           in Bracket Notation:

                "Couldn't access datanode [sprintf,%10x=~[%s~],_1,_2]!\n"


                Couldn't access datanode      Stuff=[thangamabob]!

           Currently this just takes the last bit of

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           "ref($language)", turns underscores to dashes, and
           returns it.  So if $language is an object of class
           Hee::HOO::Haw::en_us, $language->language_tag()
           returns "en-us".  (Yes, the usual representation for
           that language tag is "en-US", but case is never con-
           sidered meaningful in language-tag comparison.)

           You may override this as you like; Maketext doesn't
           use it for anything.

           Currently this isn't used for anything, but it's pro-
           vided (with default value of "(ref($language) && $lan-
           guage->{'encoding'})) or "iso-8859-1"" ) as a sort of
           suggestion that it may be useful/necessary to associ-
           ate encodings with your language handles (whether on a
           per-class or even per-handle basis.)

       Language Handle Attributes and Internals

       A language handle is a flyweight object -- i.e., it
       doesn't (necessarily) carry any data of interest, other
       than just being a member of whatever class it belongs to.

       A language handle is implemented as a blessed hash.  Sub-
       classes of yours can store whatever data you want in the
       hash.  Currently the only hash entry used by any crucial
       Maketext method is "fail", so feel free to use anything
       else as you like.

       Remember: Don't be afraid to read the Maketext source if
       there's any point on which this documentation is unclear.
       This documentation is vastly longer than the module source

       These are Locale::Maketext's assumptions about the class
       hierarchy formed by all your language classes:

       o   You must have a project base class, which you load,
           and which you then use as the first argument in the
           call to YourProjClass->get_handle(...).  It should
           derive (whether directly or indirectly) from
           Locale::Maketext.  It doesn't matter how you name this
           class, altho assuming this is the localization compo-
           nent of your Super Mega Program, good names for your
           project class might be SuperMegaProgram::Localization,
           SuperMegaProgram::L10N, SuperMegaProgram::I18N, Super-
           MegaProgram::International, or even SuperMegaPro-
           gram::Languages or SuperMegaProgram::Messages.

       o   Language classes are what YourProjClass->get_handle
           will try to load.  It will look for them by taking
           each language-tag (skipping it if it doesn't look like

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           a language-tag or locale-tag!), turning it to all low-
           ercase, turning and dashes to underscores, and append-
           ing it to YourProjClass . "::".  So this:

             $lh = YourProjClass->get_handle(
               'en-US', 'fr', 'kon', 'i-klingon', 'i-klingon-romanized'

           will try loading the classes YourProjClass::en_us
           (note lowercase!), YourProjClass::fr, YourProj-
           Class::kon, YourProjClass::i_klingon and YourProj-
           Class::i_klingon_romanized.  (And it'll stop at the
           first one that actually loads.)

       o   I assume that each language class derives (directly or
           indirectly) from your project class, and also defines
           its @ISA, its %Lexicon, or both.  But I anticipate no
           dire consequences if these assumptions do not hold.

       o   Language classes may derive from other language
           classes (altho they should have "use Thatclassname" or
           "use base qw(...classes...)").  They may derive from
           the project class.  They may derive from some other
           class altogether.  Or via multiple inheritance, it may
           derive from any mixture of these.

       o   I foresee no problems with having multiple inheritance
           in your hierarchy of language classes.  (As usual,
           however, Perl will complain bitterly if you have a
           cycle in the hierarchy: i.e., if any class is its own

       A typical %Lexicon entry is meant to signify a phrase,
       taking some number (0 or more) of parameters.  An entry is
       meant to be accessed by via a string key in $lh->make-
       text(key, ...parameters...), which should return a string
       that is generally meant for be used for "output" to the
       user -- regardless of whether this actually means printing
       to STDOUT, writing to a file, or putting into a GUI wid-

       While the key must be a string value (since that's a basic
       restriction that Perl places on hash keys), the value in
       the lexicon can currently be of several types: a defined
       scalar, scalarref, or coderef.  The use of these is
       explained above, in the section 'The "maketext" Method',
       and Bracket Notation for strings is discussed in the next

       While you can use arbitrary unique IDs for lexicon keys
       (like "_min_larger_max_error"), it is often useful for if
       an entry's key is itself a valid value, like this example
       error message:

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         "Minimum ([_1]) is larger than maximum ([_2])!\n",

       Compare this code that uses an arbitrary ID...

         die $lh->maketext( "_min_larger_max_error", $min, $max )
          if $min > $max;

       ...to this code that uses a key-as-value:

         die $lh->maketext(
          "Minimum ([_1]) is larger than maximum ([_2])!\n",
          $min, $max
         ) if $min > $max;

       The second is, in short, more readable.  In particular,
       it's obvious that the number of parameters you're feeding
       to that phrase (two) is the number of parameters that it
       wants to be fed.  (Since you see _1 and a _2 being used in
       the key there.)

       Also, once a project is otherwise complete and you start
       to localize it, you can scrape together all the various
       keys you use, and pass it to a translator; and then the
       translator's work will go faster if what he's presented is

        "Minimum ([_1]) is larger than maximum ([_2])!\n",
         => "",   # fill in something here, Jacques!

       rather than this more cryptic mess:

         => "",   # fill in something here, Jacques

       I think that keys as lexicon values makes the completed
       lexicon entries more readable:

        "Minimum ([_1]) is larger than maximum ([_2])!\n",
         => "Le minimum ([_1]) est plus grand que le maximum ([_2])!\n",

       Also, having valid values as keys becomes very useful if
       you set up an _AUTO lexicon.  _AUTO lexicons are discussed
       in a later section.

       I almost always use keys that are themselves valid lexicon
       values.  One notable exception is when the value is quite
       long.  For example, to get the screenful of data that a
       command-line program might returns when given an unknown
       switch, I often just use a key "_USAGE_MESSAGE".  At that
       point I then go and immediately to define that lexicon
       entry in the ProjectClass::L10N::en lexicon (since English
       is always my "project language"):

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         '_USAGE_MESSAGE' => <<'EOSTUFF',
         ...long long message...

       and then I can use it as:

         getopt('oDI', \%opts) or die $lh->maketext('_USAGE_MESSAGE');

       Incidentally, note that each class's %Lexicon inherits-
       and-extends the lexicons in its superclasses.  This is not
       because these are special hashes per se, but because you
       access them via the "maketext" method, which looks for
       entries across all the %Lexicon's in a language class and
       all its ancestor classes.  (This is because the idea of
       "class data" isn't directly implemented in Perl, but is
       instead left to individual class-systems to implement as
       they see fit..)

       Note that you may have things stored in a lexicon besides
       just phrases for output:  for example, if your program
       takes input from the keyboard, asking a "(Y/N)" question,
       you probably need to know what equivalent of "Y[es]/N[o]"
       is in whatever language.  You probably also need to know
       what the equivalents of the answers "y" and "n" are.  You
       can store that information in the lexicon (say, under the
       keys "~answer_y" and "~answer_n", and the long forms as
       "~answer_yes" and "~answer_no", where "~" is just an ad-
       hoc character meant to indicate to programmers/translators
       that these are not phrases for output).

       Or instead of storing this in the language class's lexi-
       con, you can (and, in some cases, really should) represent
       the same bit of knowledge as code is a method in the lan-
       guage class.  (That leaves a tidy distinction between the
       lexicon as the things we know how to say, and the rest of
       the things in the lexicon class as things that we know how
       to do.)  Consider this example of a processor for
       responses to French "oui/non" questions:

         sub y_or_n {
           return undef unless defined $_[1] and length $_[1];
           my $answer = lc $_[1];  # smash case
           return 1 if $answer eq 'o' or $answer eq 'oui';
           return 0 if $answer eq 'n' or $answer eq 'non';
           return undef;

       ...which you'd then call in a construct like this:

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         my $response;
         until(defined $response) {
           print $lh->maketext("Open the pod bay door (y/n)? ");
           $response = $lh->y_or_n( get_input_from_keyboard_somehow() );
         if($response) { $pod_bay_door->open()         }
         else          { $pod_bay_door->leave_closed() }

       Other data worth storing in a lexicon might be things like
       filenames for language-targetted resources:

           => "/styles/en_us/main_splash.png",
           => "/styles/en_us/main_splash.incl",
           => "/styles/en_us/",
           => "/styles/en_us/hey_there.wav",
          => "left_arrow.png",
          => "right_arrow.png",
         # In some other languages, left equals
         #  BACKwards, and right is FOREwards.

       You might want to do the same thing for expressing key
       bindings or the like (since hardwiring "q" as the binding
       for the function that quits a screen/menu/program is use-
       ful only if your language happens to associate "q" with

       Bracket Notation is a crucial feature of Locale::Maketext.
       I mean Bracket Notation to provide a replacement for
       sprintf formatting.  Everything you do with Bracket Nota-
       tion could be done with a sub block, but bracket notation
       is meant to be much more concise.

       Bracket Notation is a like a miniature "template" system
       (in the sense of Text::Template, not in the sense of C++
       templates), where normal text is passed thru basically as
       is, but text is special regions is specially interpreted.
       In Bracket Notation, you use brackets ("[...]" -- not
       "{...}"!) to note sections that are specially interpreted.

       For example, here all the areas that are taken literally
       are underlined with a "^", and all the in-bracket special
       regions are underlined with an X:

         "Minimum ([_1]) is larger than maximum ([_2])!\n",
          ^^^^^^^^^ XX ^^^^^^^^^^^^^^^^^^^^^^^^^^ XX ^^^^

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       When that string is compiled from bracket notation into a
       real Perl sub, it's basically turned into:

         sub {
           my $lh = $_[0];
           my @params = @_;
           return join '',
             "Minimum (",
             ...some code here...
             ") is larger than maximum (",
             ...some code here...
         # to be called by $lh->maketext(KEY, params...)

       In other words, text outside bracket groups is turned into
       string literals.  Text in brackets is rather more complex,
       and currently follows these rules:

       o   Bracket groups that are empty, or which consist only
           of whitespace, are ignored.  (Examples: "[]", "[
           ]", or a [ and a ] with returns and/or tabs and/or
           spaces between them.

           Otherwise, each group is taken to be a comma-separated
           group of items, and each item is interpreted as fol-

       o   An item that is "_digits" or "_-digits" is interpreted
           as $_[value].  I.e., "_1" is becomes with $_[1], and
           "_-3" is interpreted as $_[-3] (in which case @_
           should have at least three elements in it).  Note that
           $_[0] is the language handle, and is typically not
           named directly.

       o   An item "_*" is interpreted to mean "all of @_ except
           $_[0]".  I.e., @_[1..$#_].  Note that this is an empty
           list in the case of calls like $lh->maketext(key)
           where there are no parameters (except $_[0], the lan-
           guage handle).

       o   Otherwise, each item is interpreted as a string lit-

       The group as a whole is interpreted as follows:

       o   If the first item in a bracket group looks like a
           method name, then that group is interpreted like this:

               ...rest of items in this group...

       o   If the first item in a bracket group is "*", it's

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           taken as shorthand for the so commonly called "quant"
           method.  Similarly, if the first item in a bracket
           group is "#", it's taken to be shorthand for "numf".

       o   If the first item in a bracket group is empty-string,
           or "_*" or "_digits" or "_-digits", then that group is
           interpreted as just the interpolation of all its

               ...rest of items in this group...

           Examples:  "[_1]" and "[,_1]", which are synonymous;
           and ""[,ID-(,_4,-,_2,)]"", which compiles as "join "",
           "ID-(", $_[4], "-", $_[2], ")"".

       o   Otherwise this bracket group is invalid.  For example,
           in the group "[!@#,whatever]", the first item "!@#" is
           neither empty-string, "_number", "_-number", "_*", nor
           a valid method name; and so Locale::Maketext will
           throw an exception of you try compiling an expression
           containing this bracket group.

       Note, incidentally, that items in each group are
       comma-separated, not "/\s*,\s*/"-separated.  That is, you
       might expect that this bracket group:

         "Hoohah [foo, _1 , bar ,baz]!"

       would compile to this:

         sub {
           my $lh = $_[0];
           return join '',
             "Hoohah ",
             $lh->foo( $_[1], "bar", "baz"),

       But it actually compiles as this:

         sub {
           my $lh = $_[0];
           return join '',
             "Hoohah ",
             $lh->foo(" _1 ", " bar ", "baz"),  #!!!

       In the notation discussed so far, the characters "[" and
       "]" are given special meaning, for opening and closing
       bracket groups, and "," has a special meaning inside
       bracket groups, where it separates items in the group.

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       This begs the question of how you'd express a literal "["
       or "]" in a Bracket Notation string, and how you'd express
       a literal comma inside a bracket group.  For this purpose
       I've adopted "~" (tilde) as an escape character:  "~["
       means a literal '[' character anywhere in Bracket Notation
       (i.e., regardless of whether you're in a bracket group or
       not), and ditto for "~]" meaning a literal ']', and "~,"
       meaning a literal comma.  (Altho "," means a literal comma
       outside of bracket groups -- it's only inside bracket
       groups that commas are special.)

       And on the off chance you need a literal tilde in a
       bracket expression, you get it with "~~".

       Currently, an unescaped "~" before a character other than
       a bracket or a comma is taken to mean just a "~" and that
       character.  I.e., "~X" means the same as "~~X" -- i.e.,
       one literal tilde, and then one literal "X".  However, by
       using "~X", you are assuming that no future version of
       Maketext will use "~X" as a magic escape sequence.  In
       practice this is not a great problem, since first off you
       can just write "~~X" and not worry about it; second off, I
       doubt I'll add lots of new magic characters to bracket
       notation; and third off, you aren't likely to want literal
       "~" characters in your messages anyway, since it's not a
       character with wide use in natural language text.

       Brackets must be balanced -- every openbracket must have
       one matching closebracket, and vice versa.  So these are
       all invalid:

         "I ate [quant,_1,rhubarb pie."
         "I ate [quant,_1,rhubarb pie[."
         "I ate quant,_1,rhubarb pie]."
         "I ate quant,_1,rhubarb pie[."

       Currently, bracket groups do not nest.  That is, you can-
       not say:

         "Foo [bar,baz,[quux,quuux]]\n";

       If you need a notation that's that powerful, use normal

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         %Lexicon = (
           "some_key" => sub {
             my $lh = $_[0];
             join '',
               "Foo ",
               $lh->bar('baz', $lh->quux('quuux')),

       Or write the "bar" method so you don't need to pass it the
       output from calling quux.

       I do not anticipate that you will need (or particularly
       want) to nest bracket groups, but you are welcome to email
       me with convincing (real-life) arguments to the contrary.

       If maketext goes to look in an individual %Lexicon for an
       entry for key (where key does not start with an under-
       score), and sees none, but does see an entry of "_AUTO" =>
       some_true_value, then we actually define $Lexicon{key} =
       key right then and there, and then use that value as if it
       had been there all along.  This happens before we even
       look in any superclass %Lexicons!

       (This is meant to be somewhat like the AUTOLOAD mechanism
       in Perl's function call system -- or, looked at another
       way, like the AutoLoader module.)

       I can picture all sorts of circumstances where you just do
       not want lookup to be able to fail (since failing normally
       means that maketext throws a "die", altho see the next
       section for greater control over that).  But here's one
       circumstance where _AUTO lexicons are meant to be espe-
       cially useful:

       As you're writing an application, you decide as you go
       what messages you need to emit.  Normally you'd go to
       write this:

         if(-e $filename) {
         } else {
           print "Couldn't find file \"$filename\"!\n";

       but since you anticipate localizing this, you write:

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         use ThisProject::I18N;
         my $lh = ThisProject::I18N->get_handle();
          # For the moment, assume that things are set up so
          # that we load class ThisProject::I18N::en
          # and that that's the class that $lh belongs to.
         if(-e $filename) {
         } else {
           print $lh->maketext(
             "Couldn't find file \"[_1]\"!\n", $filename

       Now, right after you've just written the above lines,
       you'd normally have to go open the file ThisPro-
       ject/I18N/en.pm, and immediately add an entry:

         "Couldn't find file \"[_1]\"!\n"
         => "Couldn't find file \"[_1]\"!\n",

       But I consider that somewhat of a distraction from the
       work of getting the main code working -- to say nothing of
       the fact that I often have to play with the program a few
       times before I can decide exactly what wording I want in
       the messages (which in this case would require me to go
       changing three lines of code: the call to maketext with
       that key, and then the two lines in ThisPro-

       However, if you set "_AUTO => 1" in the %Lexicon in, This-
       Project/I18N/en.pm (assuming that English (en) is the lan-
       guage that all your programmers will be using for this
       project's internal message keys), then you don't ever have
       to go adding lines like this

         "Couldn't find file \"[_1]\"!\n"
         => "Couldn't find file \"[_1]\"!\n",

       to ThisProject/I18N/en.pm, because if _AUTO is true there,
       then just looking for an entry with the key "Couldn't find
       file \"[_1]\"!\n" in that lexicon will cause it to be
       added, with that value!

       Note that the reason that keys that start with "_" are
       immune to _AUTO isn't anything generally magical about the
       underscore character -- I just wanted a way to have most
       lexicon keys be autoable, except for possibly a few, and I
       arbitrarily decided to use a leading underscore as a sig-
       nal to distinguish those few.

       If you call $lh->maketext(key, ...parameters...), and
       there's no entry key in $lh's class's %Lexicon, nor in the

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       superclass %Lexicon hash, and if we can't auto-make key
       (because either it starts with a "_", or because none of
       its lexicons have "_AUTO => 1,"), then we have failed to
       find a normal way to maketext key.  What then happens in
       these failure conditions, depends on the $lh object "fail"

       If the language handle has no "fail" attribute, maketext
       will simply throw an exception (i.e., it calls "die", men-
       tioning the key whose lookup failed, and naming the line
       number where the calling $lh->maketext(key,...) was.

       If the language handle has a "fail" attribute whose value
       is a coderef, then $lh->maketext(key,...params...) gives
       up and calls:

         return &{$that_subref}($lh, $key, @params);

       Otherwise, the "fail" attribute's value should be a string
       denoting a method name, so that $lh->make-
       text(key,...params...) can give up with:

         return $lh->$that_method_name($phrase, @params);

       The "fail" attribute can be accessed with the "fail_with"

         # Set to a coderef:
         $lh->fail_with( \&failure_handler );

         # Set to a method name:
         $lh->fail_with( 'failure_method' );

         # Set to nothing (i.e., so failure throws a plain exception)
         $lh->fail_with( undef );

         # Simply read:
         $handler = $lh->fail_with();

       Now, as to what you may want to do with these handlers:
       Maybe you'd want to log what key failed for what class,
       and then die.  Maybe you don't like "die" and instead you
       want to send the error message to STDOUT (or wherever) and
       then merely "exit()".

       Or maybe you don't want to "die" at all!  Maybe you could
       use a handler like this:

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         # Make all lookups fall back onto an English value,
         #  but after we log it for later fingerpointing.
         my $lh_backup = ThisProject->get_handle('en');
         open(LEX_FAIL_LOG, ">>wherever/lex.log") || die "GNAARGH $!";
         sub lex_fail {
           my($failing_lh, $key, $params) = @_;
           print LEX_FAIL_LOG scalar(localtime), "\t",
              ref($failing_lh), "\t", $key, "\n";
           return $lh_backup->maketext($key,@params);

       Some users have expressed that they think this whole mech-
       anism of having a "fail" attribute at all, seems a rather
       pointless complication.  But I want Locale::Maketext to be
       usable for software projects of any scale and type; and
       different software projects have different ideas of what
       the right thing is to do in failure conditions.  I could
       simply say that failure always throws an exception, and
       that if you want to be careful, you'll just have to wrap
       every call to $lh->maketext in an eval { }.  However, I
       want programmers to reserve the right (via the "fail"
       attribute) to treat lookup failure as something other than
       an exception of the same level of severity as a config
       file being unreadable, or some essential resource being

       One possibly useful value for the "fail" attribute is the
       method name "failure_handler_auto".  This is a method
       defined in class Locale::Maketext itself.  You set it


       Then when you call $lh->maketext(key, ...parameters...)
       and there's no key in any of those lexicons, maketext
       gives up with

         return $lh->failure_handler_auto($key, @params);

       But failure_handler_auto, instead of dying or anything,
       compiles $key, caching it in $lh->{'failure_lex'}{$key} =
       $complied, and then calls the compiled value, and returns
       that.  (I.e., if $key looks like bracket notation, $com-
       piled is a sub, and we return &{$compiled}(@params); but
       if $key is just a plain string, we just return that.)

       The effect of using "failure_auto_handler" is like an AUTO
       lexicon, except that it 1) compiles $key even if it starts
       with "_", and 2) you have a record in the new hashref
       $lh->{'failure_lex'} of all the keys that have failed for
       this object.  This should avoid your program dying -- as
       long as your keys aren't actually invalid as bracket code,
       and as long as they don't try calling methods that don't

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       "failure_auto_handler" may not be exactly what you want,
       but I hope it at least shows you that maketext failure can
       be mitigated in any number of very flexible ways.  If you
       can formalize exactly what you want, you should be able to
       express that as a failure handler.  You can even make it
       default for every object of a given class, by setting it
       in that class's init:

         sub init {
           my $lh = $_[0];  # a newborn handle
         sub my_clever_failure_handler {
           ...you clever things here...

       Here is a brief checklist on how to use Maketext to local-
       ize applications:

       o   Decide what system you'll use for lexicon keys.  If
           you insist, you can use opaque IDs (if you're nostal-
           gic for "catgets"), but I have better suggestions in
           the section "Entries in Each Lexicon", above.  Assum-
           ing you opt for meaningful keys that double as values
           (like "Minimum ([_1]) is larger than maximum
           ([_2])!\n"), you'll have to settle on what language
           those should be in.  For the sake of argument, I'll
           call this English, specifically American English,

       o   Create a class for your localization project.  This is
           the name of the class that you'll use in the idiom:

             use Projname::L10N;
             my $lh = Projname::L10N->get_handle(...) || die "Language?";

           Assuming your call your class Projname::L10N, create a
           class consisting minimally of:

             package Projname::L10N;
             use base qw(Locale::Maketext);
             ...any methods you might want all your languages to share...

             # And, assuming you want the base class to be an _AUTO lexicon,
             # as is discussed a few sections up:


       o   Create a class for the language your internal keys are
           in.  Name the class after the language-tag for that
           language, in lowercase, with dashes changed to

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           underscores.  Assuming your project's first language
           is US English, you should call this Proj-
           name::L10N::en_us.  It should consist minimally of:

             package Projname::L10N::en_us;
             use base qw(Projname::L10N);
             %Lexicon = (
               '_AUTO' => 1,

           (For the rest of this section, I'll assume that this
           "first language class" of Projname::L10N::en_us has
           _AUTO lexicon.)

       o   Go and write your program.  Everywhere in your program
           where you would say:

             print "Foobar $thing stuff\n";

           instead do it thru maketext, using no variable inter-
           polation in the key:

             print $lh->maketext("Foobar [_1] stuff\n", $thing);

           If you get tired of constantly saying "print
           $lh->maketext", consider making a functional wrapper
           for it, like so:

             use Projname::L10N;
             use vars qw($lh);
             $lh = Projname::L10N->get_handle(...) || die "Language?";
             sub pmt (@) { print( $lh->maketext(@_)) }
              # "pmt" is short for "Print MakeText"
             $Carp::Verbose = 1;
              # so if maketext fails, we see made the call to pmt

           Besides whole phrases meant for output, anything lan-
           guage-dependent should be put into the class Proj-
           name::L10N::en_us, whether as methods, or as lexicon
           entries -- this is discussed in the section "Entries
           in Each Lexicon", above.

       o   Once the program is otherwise done, and once its
           localization for the first language works right (via
           the data and methods in Projname::L10N::en_us), you
           can get together the data for translation.  If your
           first language lexicon isn't an _AUTO lexicon, then
           you already have all the messages explicitly in the
           lexicon (or else you'd be getting exceptions thrown
           when you call $lh->maketext to get messages that
           aren't in there).  But if you were (advisedly) lazy
           and are using an _AUTO lexicon, then you've got to
           make a list of all the phrases that you've so far been

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           letting _AUTO generate for you.  There are very many
           ways to assemble such a list.  The most straightfor-
           ward is to simply grep the source for every occurrence
           of "maketext" (or calls to wrappers around it, like
           the above "pmt" function), and to log the following

       o   You may at this point want to consider whether the
           your base class (Projname::L10N) that all lexicons
           inherit from (Projname::L10N::en, Projname::L10N::es,
           etc.) should be an _AUTO lexicon.  It may be true that
           in theory, all needed messages will be in each lan-
           guage class; but in the presumably unlikely or "impos-
           sible" case of lookup failure, you should consider
           whether your program should throw an exception, emit
           text in English (or whatever your project's first lan-
           guage is), or some more complex solution as described
           in the section "Controlling Lookup Failure", above.

       o   Submit all messages/phrases/etc. to translators.

           (You may, in fact, want to start with localizing to
           one other language at first, if you're not sure that
           you've property abstracted the language-dependent
           parts of your code.)

           Translators may request clarification of the situation
           in which a particular phrase is found.  For example,
           in English we are entirely happy saying "n files
           found", regardless of whether we mean "I looked for
           files, and found n of them" or the rather distinct
           situation of "I looked for something else (like lines
           in files), and along the way I saw n files."  This may
           involve rethinking things that you thought quite
           clear: should "Edit" on a toolbar be a noun ("edit-
           ing") or a verb ("to edit")?  Is there already a con-
           ventionalized way to express that menu option, sepa-
           rate from the target language's normal word for "to

           In all cases where the very common phenomenon of quan-
           tification (saying "N files", for any value of N) is
           involved, each translator should make clear what
           dependencies the number causes in the sentence.  In
           many cases, dependency is limited to words adjacent to
           the number, in places where you might expect them ("I
           found the-?PLURAL N empty-?PLURAL directory-?PLURAL"),
           but in some cases there are unexpected dependencies
           ("I found-?PLURAL ..."!) as well as long-distance
           dependencies "The N directory-?PLURAL could not be

           Remind the translators to consider the case where N is
           0: "0 files found" isn't exactly natural-sounding in

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           any language, but it may be unacceptable in many -- or
           it may condition special kinds of agreement (similar
           to English "I didN'T find ANY files").

           Remember to ask your translators about numeral format-
           ting in their language, so that you can override the
           "numf" method as appropriate.  Typical variables in
           number formatting are:  what to use as a decimal point
           (comma? period?); what to use as a thousands separator
           (space? nonbreaking space? comma? period? small mid-
           dot? prime? apostrophe?); and even whether the so-
           called "thousands separator" is actually for every
           third digit -- I've heard reports of two hundred thou-
           sand being expressible as "2,00,000" for some Indian
           (Subcontinental) languages, besides the less surpris-
           ing "200 000", "200.000", "200,000", and "200'000".
           Also, using a set of numeral glyphs other than the
           usual ASCII "0"-"9" might be appreciated, as via
           "tr/0-9/\x{0966}-\x{096F}/" for getting digits in
           Devanagari script (for Hindi, Konkani, others).

           The basic "quant" method that Locale::Maketext pro-
           vides should be good for many languages.  For some
           languages, it might be useful to modify it (or its
           constituent "numerate" method) to take a plural form
           in the two-argument call to "quant" (as in
           "[quant,_1,files]") if it's all-around easier to infer
           the singular form from the plural, than to infer the
           plural form from the singular.

           But for other languages (as is discussed at length in
           Locale::Maketext::TPJ13), simple "quant"/"numerify" is
           not enough.  For the particularly problematic Slavic
           languages, what you may need is a method which you
           provide with the number, the citation form of the noun
           to quantify, and the case and gender that the sen-
           tence's syntax projects onto that noun slot.  The
           method would then be responsible for determining what
           grammatical number that numeral projects onto its noun
           phrase, and what case and gender it may override the
           normal case and gender with; and then it would look up
           the noun in a lexicon providing all needed inflected

       o   You may also wish to discuss with the translators the
           question of how to relate different subforms of the
           same language tag, considering how this reacts with
           "get_handle"'s treatment of these.  For example, if a
           user accepts interfaces in "en, fr", and you have
           interfaces available in "en-US" and "fr", what should
           they get?  You may wish to resolve this by establish-
           ing that "en" and "en-US" are effectively synonymous,
           by having one class zero-derive from the other.

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           For some languages this issue may never come up (Dan-
           ish is rarely expressed as "da-DK", but instead is
           just "da").  And for other languages, the whole con-
           cept of a "generic" form may verge on being uselessly
           vague, particularly for interfaces involving voice
           media in forms of Arabic or Chinese.

       o   Once you've localized your program/site/etc. for all
           desired languages, be sure to show the result (whether
           live, or via screenshots) to the translators.  Once
           they approve, make every effort to have it then
           checked by at least one other speaker of that lan-
           guage.  This holds true even when (or especially when)
           the translation is done by one of your own program-
           mers.  Some kinds of systems may be harder to find
           testers for than others, depending on the amount of
           domain-specific jargon and concepts involved -- it's
           easier to find people who can tell you whether they
           approve of your translation for "delete this message"
           in an email-via-Web interface, than to find people who
           can give you an informed opinion on your translation
           for "attribute value" in an XML query tool's inter-

       I recommend reading all of these:

       Locale::Maketext::TPJ13 -- my The Perl Journal article
       about Maketext.  It explains many important concepts
       underlying Locale::Maketext's design, and some insight
       into why Maketext is better than the plain old approach of
       just having message catalogs that are just databases of
       sprintf formats.

       File::Findgrep is a sample application/module that uses
       Locale::Maketext to localize its messages.  For a larger
       internationalized system, see also Apache::MP3.



       RFC 3066, Tags for the Identification of Languages, as at

       RFC 2277, IETF Policy on Character Sets and Languages is
       at http://sunsite.dk/RFC/rfc/rfc2277.html -- much of it is
       just things of interest to protocol designers, but it
       explains some basic concepts, like the distinction between
       locales and language-tags.

       The manual for GNU "gettext".  The gettext dist is avail-
       able in "ftp://prep.ai.mit.edu/pub/gnu/" -- get a recent
       gettext tarball and look in its "doc/" directory, there's

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       an easily browsable HTML version in there.  The gettext
       documentation asks lots of questions worth thinking about,
       even if some of their answers are sometimes wonky, partic-
       ularly where they start talking about pluralization.

       The Locale/Maketext.pm source.  Obverse that the module is
       much shorter than its documentation!

       Copyright (c) 1999-2004 Sean M. Burke.  All rights

       This library is free software; you can redistribute it
       and/or modify it under the same terms as Perl itself.

       This program is distributed in the hope that it will be
       useful, but without any warranty; without even the implied
       warranty of merchantability or fitness for a particular

       Sean M. Burke "sburkeATcpan.org"

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