NAME

  JSON - JSON (JavaScript Object Notation) encoder/decoder

SYNOPSIS

   use JSON; # imports encode_json, decode_json, to_json and from_json.

   # simple and fast interfaces (expect/generate UTF-8)

   $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;

   $perl_hash_or_arrayref  = decode_json $utf8_encoded_json_text;

   # OO-interface

   $json = JSON->new->allow_nonref;

   $json_text   = $json->encode( $perl_scalar );

   $perl_scalar = $json->decode( $json_text );

   $pretty_printed = $json->pretty->encode( $perl_scalar ); # pretty-printing

VERSION

      2.93

DESCRIPTION

  This module is a thin wrapper for JSON::XS-compatible modules with

  a few additional features. All the backend modules convert a Perl

  data structure to a JSON text as of RFC4627 (which we know is

  obsolete but we still stick to; see below for an option to support

  part of RFC7159) and vice versa. This module uses JSON::XS by

  default, and when JSON::XS is not available, this module falls

  back on JSON::PP, which is in the Perl core since 5.14. If

  JSON::PP is not available either, this module then falls back on

  JSON::backportPP (which is actually JSON::PP in a different .pm

  file) bundled in the same distribution as this module. You can

  also explicitly specify to use Cpanel::JSON::XS, a fork of

  JSON::XS by Reini Urban.

  All these backend modules have slight incompatibilities between

  them, including extra features that other modules don't support,

  but as long as you use only common features (most important ones

  are described below), migration from backend to backend should be

  reasonably easy. For details, see each backend module you use.

CHOOSING BACKEND

  This module respects an environmental variable called

  "PERL_JSON_BACKEND" when it decides a backend module to use. If

  this environmental variable is not set, it tries to load JSON::XS,

  and if JSON::XS is not available, it falls back on JSON::PP, and

  then JSON::backportPP if JSON::PP is not available either.

  If you always don't want it to fall back on pure perl modules, set

  the variable like this ("export" may be "setenv", "set" and the

  likes, depending on your environment):

    > export PERL_JSON_BACKEND=JSON::XS

  If you prefer Cpanel::JSON::XS to JSON::XS, then:

    > export PERL_JSON_BACKEND=Cpanel::JSON::XS,JSON::XS,JSON::PP

  You may also want to set this variable at the top of your test

  files, in order not to be bothered with incompatibilities between

  backends (you need to wrap this in "BEGIN", and set before

  actually "use"-ing JSON module, as it decides its backend as soon

  as it's loaded):

    BEGIN { $ENV{PERL_JSON_BACKEND}='JSON::backportPP'; }

    use JSON;

USING OPTIONAL FEATURES

  There are a few options you can set when you "use" this module:

  -support_by_pp

         BEGIN { $ENV{PERL_JSON_BACKEND} = 'JSON::XS' }

         use JSON -support_by_pp;

         my $json = JSON->new;

         # escape_slash is for JSON::PP only.

         $json->allow_nonref->escape_slash->encode("/");

      With this option, this module loads its pure perl backend

      along with its XS backend (if available), and lets the XS

      backend to watch if you set a flag only JSON::PP supports.

      When you do, the internal JSON::XS object is replaced with a

      newly created JSON::PP object with the setting copied from the

      XS object, so that you can use JSON::PP flags (and its slower

      "decode"/"encode" methods) from then on. In other words, this

      is not something that allows you to hook JSON::XS to change

      its behavior while keeping its speed. JSON::XS and JSON::PP

      objects are quite different (JSON::XS object is a blessed

      scalar reference, while JSON::PP object is a blessed hash

      reference), and can't share their internals.

      To avoid needless overhead (by copying settings), you are

      advised not to use this option and just to use JSON::PP

      explicitly when you need JSON::PP features.

  -convert_blessed_universally

         use JSON -convert_blessed_universally;

         my $json = JSON->new->allow_nonref->convert_blessed;

         my $object = bless {foo => 'bar'}, 'Foo';

         $json->encode($object); # => {"foo":"bar"}

      JSON::XS-compatible backend modules don't encode blessed

      objects by default (except for their boolean values, which are

      typically blessed JSON::PP::Boolean objects). If you need to

      encode a data structure that may contain objects, you usually

      need to look into the structure and replace objects with

      alternative non-blessed values, or enable "convert_blessed"

      and provide a "TO_JSON" method for each object's (base) class

      that may be found in the structure, in order to let the

      methods replace the objects with whatever scalar values the

      methods return.

      If you need to serialise data structures that may contain

      arbitrary objects, it's probably better to use other

      serialisers (such as Sereal or Storable for example), but if

      you do want to use this module for that purpose,

      "-convert_blessed_universally" option may help, which tweaks

      "encode" method of the backend to install "UNIVERSAL::TO_JSON"

      method (locally) before encoding, so that all the objects that

      don't have their own "TO_JSON" method can fall back on the

      method in the "UNIVERSAL" namespace. Note that you still need

      to enable "convert_blessed" flag to actually encode objects in

      a data structure, and "UNIVERSAL::TO_JSON" method installed by

      this option only converts blessed hash/array references into

      their unblessed clone (including private keys/values that are

      not supposed to be exposed). Other blessed references will be

      converted into null.

      This feature is experimental and may be removed in the future.

  -no_export

      When you don't want to import functional interfaces from a

      module, you usually supply "()" to its "use" statement.

          use JSON (); # no functional interfaces

      If you don't want to import functional interfaces, but you

      also want to use any of the above options, add "-no_export" to

      the option list.

         # no functional interfaces, while JSON::PP support is enabled.

         use JSON -support_by_pp, -no_export;

FUNCTIONAL INTERFACE

  This section is taken from JSON::XS. "encode_json" and

  "decode_json" are exported by default.

  This module also exports "to_json" and "from_json" for backward

  compatibility. These are slower, and may expect/generate different

  stuff from what "encode_json" and "decode_json" do, depending on

  their options. It's better just to use Object-Oriented interfaces

  than using these two functions.

 encode_json

      $json_text = encode_json $perl_scalar

  Converts the given Perl data structure to a UTF-8 encoded, binary

  string (that is, the string contains octets only). Croaks on

  error.

  This function call is functionally identical to:

      $json_text = JSON->new->utf8->encode($perl_scalar)

  Except being faster.

 decode_json

      $perl_scalar = decode_json $json_text

  The opposite of "encode_json": expects an UTF-8 (binary) string

  and tries to parse that as an UTF-8 encoded JSON text, returning

  the resulting reference. Croaks on error.

  This function call is functionally identical to:

      $perl_scalar = JSON->new->utf8->decode($json_text)

  Except being faster.

 to_json

     $json_text = to_json($perl_scalar[, $optional_hashref])

  Converts the given Perl data structure to a Unicode string by

  default. Croaks on error.

  Basically, this function call is functionally identical to:

     $json_text = JSON->new->encode($perl_scalar)

  Except being slower.

  You can pass an optional hash reference to modify its behavior,

  but that may change what "to_json" expects/generates (see

  "ENCODING/CODESET FLAG NOTES" for details).

     $json_text = to_json($perl_scalar, {utf8 => 1, pretty => 1})

     # => JSON->new->utf8(1)->pretty(1)->encode($perl_scalar)

 from_json

     $perl_scalar = from_json($json_text[, $optional_hashref])

  The opposite of "to_json": expects a Unicode string and tries to

  parse it, returning the resulting reference. Croaks on error.

  Basically, this function call is functionally identical to:

      $perl_scalar = JSON->new->decode($json_text)

  You can pass an optional hash reference to modify its behavior,

  but that may change what "from_json" expects/generates (see

  "ENCODING/CODESET FLAG NOTES" for details).

      $perl_scalar = from_json($json_text, {utf8 => 1})

      # => JSON->new->utf8(1)->decode($json_text)

 JSON::is_bool

      $is_boolean = JSON::is_bool($scalar)

  Returns true if the passed scalar represents either JSON::true or

  JSON::false, two constants that act like 1 and 0 respectively and

  are also used to represent JSON "true" and "false" in Perl

  strings.

  See MAPPING, below, for more information on how JSON values are

  mapped to Perl.

COMMON OBJECT-ORIENTED INTERFACE

  This section is also taken from JSON::XS.

  The object oriented interface lets you configure your own encoding

  or decoding style, within the limits of supported formats.

 new

      $json = JSON->new

  Creates a new JSON::XS-compatible backend object that can be used

  to de/encode JSON strings. All boolean flags described below are

  by default *disabled*.

  The mutators for flags all return the backend object again and

  thus calls can be chained:

     my $json = JSON->new->utf8->space_after->encode({a => [1,2]})

     => {"a": [1, 2]}

 ascii

      $json = $json->ascii([$enable])

      $enabled = $json->get_ascii

  If $enable is true (or missing), then the "encode" method will not

  generate characters outside the code range 0..127 (which is

  ASCII). Any Unicode characters outside that range will be escaped

  using either a single \uXXXX (BMP characters) or a double

  \uHHHH\uLLLLL escape sequence, as per RFC4627. The resulting

  encoded JSON text can be treated as a native Unicode string, an

  ascii-encoded, latin1-encoded or UTF-8 encoded string, or any

  other superset of ASCII.

  If $enable is false, then the "encode" method will not escape

  Unicode characters unless required by the JSON syntax or other

  flags. This results in a faster and more compact format.

  See also the section *ENCODING/CODESET FLAG NOTES* later in this

  document.

  The main use for this flag is to produce JSON texts that can be

  transmitted over a 7-bit channel, as the encoded JSON texts will

  not contain any 8 bit characters.

    JSON->new->ascii(1)->encode([chr 0x10401])

    => ["\ud801\udc01"]

 latin1

      $json = $json->latin1([$enable])

      $enabled = $json->get_latin1

  If $enable is true (or missing), then the "encode" method will

  encode the resulting JSON text as latin1 (or iso-8859-1), escaping

  any characters outside the code range 0..255. The resulting string

  can be treated as a latin1-encoded JSON text or a native Unicode

  string. The "decode" method will not be affected in any way by

  this flag, as "decode" by default expects Unicode, which is a

  strict superset of latin1.

  If $enable is false, then the "encode" method will not escape

  Unicode characters unless required by the JSON syntax or other

  flags.

  See also the section *ENCODING/CODESET FLAG NOTES* later in this

  document.

  The main use for this flag is efficiently encoding binary data as

  JSON text, as most octets will not be escaped, resulting in a

  smaller encoded size. The disadvantage is that the resulting JSON

  text is encoded in latin1 (and must correctly be treated as such

  when storing and transferring), a rare encoding for JSON. It is

  therefore most useful when you want to store data structures known

  to contain binary data efficiently in files or databases, not when

  talking to other JSON encoders/decoders.

    JSON->new->latin1->encode (["\x{89}\x{abc}"]

    => ["\x{89}\\u0abc"]    # (perl syntax, U+abc escaped, U+89 not)

 utf8

      $json = $json->utf8([$enable])

      $enabled = $json->get_utf8

  If $enable is true (or missing), then the "encode" method will

  encode the JSON result into UTF-8, as required by many protocols,

  while the "decode" method expects to be handled an UTF-8-encoded

  string. Please note that UTF-8-encoded strings do not contain any

  characters outside the range 0..255, they are thus useful for

  bytewise/binary I/O. In future versions, enabling this option

  might enable autodetection of the UTF-16 and UTF-32 encoding

  families, as described in RFC4627.

  If $enable is false, then the "encode" method will return the JSON

  string as a (non-encoded) Unicode string, while "decode" expects

  thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or

  UTF-16) needs to be done yourself, e.g. using the Encode module.

  See also the section *ENCODING/CODESET FLAG NOTES* later in this

  document.

  Example, output UTF-16BE-encoded JSON:

    use Encode;

    $jsontext = encode "UTF-16BE", JSON->new->encode ($object);

  Example, decode UTF-32LE-encoded JSON:

    use Encode;

    $object = JSON->new->decode (decode "UTF-32LE", $jsontext);

 pretty

      $json = $json->pretty([$enable])

  This enables (or disables) all of the "indent", "space_before" and

  "space_after" (and in the future possibly more) flags in one call

  to generate the most readable (or most compact) form possible.

 indent

      $json = $json->indent([$enable])

      $enabled = $json->get_indent

  If $enable is true (or missing), then the "encode" method will use

  a multiline format as output, putting every array member or

  object/hash key-value pair into its own line, indenting them

  properly.

  If $enable is false, no newlines or indenting will be produced,

  and the resulting JSON text is guaranteed not to contain any

  "newlines".

  This setting has no effect when decoding JSON texts.

 space_before

      $json = $json->space_before([$enable])

      $enabled = $json->get_space_before

  If $enable is true (or missing), then the "encode" method will add

  an extra optional space before the ":" separating keys from values

  in JSON objects.

  If $enable is false, then the "encode" method will not add any

  extra space at those places.

  This setting has no effect when decoding JSON texts. You will also

  most likely combine this setting with "space_after".

  Example, space_before enabled, space_after and indent disabled:

     {"key" :"value"}

 space_after

      $json = $json->space_after([$enable])

      $enabled = $json->get_space_after

  If $enable is true (or missing), then the "encode" method will add

  an extra optional space after the ":" separating keys from values

  in JSON objects and extra whitespace after the "," separating

  key-value pairs and array members.

  If $enable is false, then the "encode" method will not add any

  extra space at those places.

  This setting has no effect when decoding JSON texts.

  Example, space_before and indent disabled, space_after enabled:

     {"key": "value"}

 relaxed

      $json = $json->relaxed([$enable])

      $enabled = $json->get_relaxed

  If $enable is true (or missing), then "decode" will accept some

  extensions to normal JSON syntax (see below). "encode" will not be

  affected in anyway. *Be aware that this option makes you accept

  invalid JSON texts as if they were valid!*. I suggest only to use

  this option to parse application-specific files written by humans

  (configuration files, resource files etc.)

  If $enable is false (the default), then "decode" will only accept

  valid JSON texts.

  Currently accepted extensions are:

  *   list items can have an end-comma

      JSON *separates* array elements and key-value pairs with

      commas. This can be annoying if you write JSON texts manually

      and want to be able to quickly append elements, so this

      extension accepts comma at the end of such items not just

      between them:

         [

            1,

            2, <- this comma not normally allowed

         ]

         {

            "k1": "v1",

            "k2": "v2", <- this comma not normally allowed

         }

  *   shell-style '#'-comments

      Whenever JSON allows whitespace, shell-style comments are

      additionally allowed. They are terminated by the first

      carriage-return or line-feed character, after which more

      white-space and comments are allowed.

        [

           1, # this comment not allowed in JSON

              # neither this one...

        ]

 canonical

      $json = $json->canonical([$enable])

      $enabled = $json->get_canonical

  If $enable is true (or missing), then the "encode" method will

  output JSON objects by sorting their keys. This is adding a

  comparatively high overhead.

  If $enable is false, then the "encode" method will output

  key-value pairs in the order Perl stores them (which will likely

  change between runs of the same script, and can change even within

  the same run from 5.18 onwards).

  This option is useful if you want the same data structure to be

  encoded as the same JSON text (given the same overall settings).

  If it is disabled, the same hash might be encoded differently even

  if contains the same data, as key-value pairs have no inherent

  ordering in Perl.

  This setting has no effect when decoding JSON texts.

  This setting has currently no effect on tied hashes.

 allow_nonref

      $json = $json->allow_nonref([$enable])

      $enabled = $json->get_allow_nonref

  If $enable is true (or missing), then the "encode" method can

  convert a non-reference into its corresponding string, number or

  null JSON value, which is an extension to RFC4627. Likewise,

  "decode" will accept those JSON values instead of croaking.

  If $enable is false, then the "encode" method will croak if it

  isn't passed an arrayref or hashref, as JSON texts must either be

  an object or array. Likewise, "decode" will croak if given

  something that is not a JSON object or array.

  Example, encode a Perl scalar as JSON value with enabled

  "allow_nonref", resulting in an invalid JSON text:

     JSON->new->allow_nonref->encode ("Hello, World!")

     => "Hello, World!"

 allow_unknown

      $json = $json->allow_unknown ([$enable])

      $enabled = $json->get_allow_unknown

  If $enable is true (or missing), then "encode" will *not* throw an

  exception when it encounters values it cannot represent in JSON

  (for example, filehandles) but instead will encode a JSON "null"

  value. Note that blessed objects are not included here and are

  handled separately by c<allow_nonref>.

  If $enable is false (the default), then "encode" will throw an

  exception when it encounters anything it cannot encode as JSON.

  This option does not affect "decode" in any way, and it is

  recommended to leave it off unless you know your communications

  partner.

 allow_blessed

      $json = $json->allow_blessed([$enable])

      $enabled = $json->get_allow_blessed

  See "OBJECT SERIALISATION" for details.

  If $enable is true (or missing), then the "encode" method will not

  barf when it encounters a blessed reference that it cannot convert

  otherwise. Instead, a JSON "null" value is encoded instead of the

  object.

  If $enable is false (the default), then "encode" will throw an

  exception when it encounters a blessed object that it cannot

  convert otherwise.

  This setting has no effect on "decode".

 convert_blessed

      $json = $json->convert_blessed([$enable])

      $enabled = $json->get_convert_blessed

  See "OBJECT SERIALISATION" for details.

  If $enable is true (or missing), then "encode", upon encountering

  a blessed object, will check for the availability of the "TO_JSON"

  method on the object's class. If found, it will be called in

  scalar context and the resulting scalar will be encoded instead of

  the object.

  The "TO_JSON" method may safely call die if it wants. If "TO_JSON"

  returns other blessed objects, those will be handled in the same

  way. "TO_JSON" must take care of not causing an endless recursion

  cycle (== crash) in this case. The name of "TO_JSON" was chosen

  because other methods called by the Perl core (== not by the user

  of the object) are usually in upper case letters and to avoid

  collisions with any "to_json" function or method.

  If $enable is false (the default), then "encode" will not consider

  this type of conversion.

  This setting has no effect on "decode".

 filter_json_object

      $json = $json->filter_json_object([$coderef])

  When $coderef is specified, it will be called from "decode" each

  time it decodes a JSON object. The only argument is a reference to

  the newly-created hash. If the code references returns a single

  scalar (which need not be a reference), this value (i.e. a copy of

  that scalar to avoid aliasing) is inserted into the deserialised

  data structure. If it returns an empty list (NOTE: *not* "undef",

  which is a valid scalar), the original deserialised hash will be

  inserted. This setting can slow down decoding considerably.

  When $coderef is omitted or undefined, any existing callback will

  be removed and "decode" will not change the deserialised hash in

  any way.

  Example, convert all JSON objects into the integer 5:

     my $js = JSON->new->filter_json_object (sub { 5 });

     # returns [5]

     $js->decode ('[{}]'); # the given subroutine takes a hash reference.

     # throw an exception because allow_nonref is not enabled

     # so a lone 5 is not allowed.

     $js->decode ('{"a":1, "b":2}');

 filter_json_single_key_object

      $json = $json->filter_json_single_key_object($key [=> $coderef])

  Works remotely similar to "filter_json_object", but is only called

  for JSON objects having a single key named $key.

  This $coderef is called before the one specified via

  "filter_json_object", if any. It gets passed the single value in

  the JSON object. If it returns a single value, it will be inserted

  into the data structure. If it returns nothing (not even "undef"

  but the empty list), the callback from "filter_json_object" will

  be called next, as if no single-key callback were specified.

  If $coderef is omitted or undefined, the corresponding callback

  will be disabled. There can only ever be one callback for a given

  key.

  As this callback gets called less often then the

  "filter_json_object" one, decoding speed will not usually suffer

  as much. Therefore, single-key objects make excellent targets to

  serialise Perl objects into, especially as single-key JSON objects

  are as close to the type-tagged value concept as JSON gets (it's

  basically an ID/VALUE tuple). Of course, JSON does not support

  this in any way, so you need to make sure your data never looks

  like a serialised Perl hash.

  Typical names for the single object key are "__class_whatever__",

  or "$__dollars_are_rarely_used__$" or "}ugly_brace_placement", or

  even things like "__class_md5sum(classname)__", to reduce the risk

  of clashing with real hashes.

  Example, decode JSON objects of the form "{ "__widget__" => <id>

  }" into the corresponding $WIDGET{<id>} object:

     # return whatever is in $WIDGET{5}:

     JSON

        ->new

        ->filter_json_single_key_object (__widget__ => sub {

              $WIDGET{ $_[0] }

           })

        ->decode ('{"__widget__": 5')

     # this can be used with a TO_JSON method in some "widget" class

     # for serialisation to json:

     sub WidgetBase::TO_JSON {

        my ($self) = @_;

        unless ($self->{id}) {

           $self->{id} = ..get..some..id..;

           $WIDGET{$self->{id}} = $self;

        }

        { __widget__ => $self->{id} }

     }

 max_depth

      $json = $json->max_depth([$maximum_nesting_depth])

      $max_depth = $json->get_max_depth

  Sets the maximum nesting level (default 512) accepted while

  encoding or decoding. If a higher nesting level is detected in

  JSON text or a Perl data structure, then the encoder and decoder

  will stop and croak at that point.

  Nesting level is defined by number of hash- or arrayrefs that the

  encoder needs to traverse to reach a given point or the number of

  "{" or "[" characters without their matching closing parenthesis

  crossed to reach a given character in a string.

  Setting the maximum depth to one disallows any nesting, so that

  ensures that the object is only a single hash/object or array.

  If no argument is given, the highest possible setting will be

  used, which is rarely useful.

 max_size

      $json = $json->max_size([$maximum_string_size])

      $max_size = $json->get_max_size

  Set the maximum length a JSON text may have (in bytes) where

  decoding is being attempted. The default is 0, meaning no limit.

  When "decode" is called on a string that is longer then this many

  bytes, it will not attempt to decode the string but throw an

  exception. This setting has no effect on "encode" (yet).

  If no argument is given, the limit check will be deactivated (same

  as when 0 is specified).

 encode

      $json_text = $json->encode($perl_scalar)

  Converts the given Perl value or data structure to its JSON

  representation. Croaks on error.

 decode

      $perl_scalar = $json->decode($json_text)

  The opposite of "encode": expects a JSON text and tries to parse

  it, returning the resulting simple scalar or reference. Croaks on

  error.

 decode_prefix

      ($perl_scalar, $characters) = $json->decode_prefix($json_text)

  This works like the "decode" method, but instead of raising an

  exception when there is trailing garbage after the first JSON

  object, it will silently stop parsing there and return the number

  of characters consumed so far.

  This is useful if your JSON texts are not delimited by an outer

  protocol and you need to know where the JSON text ends.

     JSON->new->decode_prefix ("[1] the tail")

     => ([1], 3)

ADDITIONAL METHODS

  The following methods are for this module only.

 backend

      $backend = $json->backend

  Since 2.92, "backend" method returns an abstract backend module

  used currently, which should be JSON::Backend::XS (which inherits

  JSON::XS or Cpanel::JSON::XS), or JSON::Backend::PP (which

  inherits JSON::PP), not to monkey-patch the actual backend module

  globally.

  If you need to know what is used actually, use "isa", instead of

  string comparison.

 is_xs

      $boolean = $json->is_xs

  Returns true if the backend inherits JSON::XS or Cpanel::JSON::XS.

 is_pp

      $boolean = $json->is_pp

  Returns true if the backend inherits JSON::PP.

 property

      $settings = $json->property()

  Returns a reference to a hash that holds all the common flag

  settings.

      $json = $json->property('utf8' => 1)

      $value = $json->property('utf8') # 1

  You can use this to get/set a value of a particular flag.

INCREMENTAL PARSING

  This section is also taken from JSON::XS.

  In some cases, there is the need for incremental parsing of JSON

  texts. While this module always has to keep both JSON text and

  resulting Perl data structure in memory at one time, it does allow

  you to parse a JSON stream incrementally. It does so by

  accumulating text until it has a full JSON object, which it then

  can decode. This process is similar to using "decode_prefix" to

  see if a full JSON object is available, but is much more efficient

  (and can be implemented with a minimum of method calls).

  This module will only attempt to parse the JSON text once it is

  sure it has enough text to get a decisive result, using a very

  simple but truly incremental parser. This means that it sometimes

  won't stop as early as the full parser, for example, it doesn't

  detect mismatched parentheses. The only thing it guarantees is

  that it starts decoding as soon as a syntactically valid JSON text

  has been seen. This means you need to set resource limits (e.g.

  "max_size") to ensure the parser will stop parsing in the presence

  if syntax errors.

  The following methods implement this incremental parser.

 incr_parse

      $json->incr_parse( [$string] ) # void context

      $obj_or_undef = $json->incr_parse( [$string] ) # scalar context

      @obj_or_empty = $json->incr_parse( [$string] ) # list context

  This is the central parsing function. It can both append new text

  and extract objects from the stream accumulated so far (both of

  these functions are optional).

  If $string is given, then this string is appended to the already

  existing JSON fragment stored in the $json object.

  After that, if the function is called in void context, it will

  simply return without doing anything further. This can be used to

  add more text in as many chunks as you want.

  If the method is called in scalar context, then it will try to

  extract exactly *one* JSON object. If that is successful, it will

  return this object, otherwise it will return "undef". If there is

  a parse error, this method will croak just as "decode" would do

  (one can then use "incr_skip" to skip the erroneous part). This is

  the most common way of using the method.

  And finally, in list context, it will try to extract as many

  objects from the stream as it can find and return them, or the

  empty list otherwise. For this to work, there must be no

  separators (other than whitespace) between the JSON objects or

  arrays, instead they must be concatenated back-to-back. If an

  error occurs, an exception will be raised as in the scalar context

  case. Note that in this case, any previously-parsed JSON texts

  will be lost.

  Example: Parse some JSON arrays/objects in a given string and

  return them.

      my @objs = JSON->new->incr_parse ("[5][7][1,2]");

 incr_text

      $lvalue_string = $json->incr_text

  This method returns the currently stored JSON fragment as an

  lvalue, that is, you can manipulate it. This *only* works when a

  preceding call to "incr_parse" in *scalar context* successfully

  returned an object. Under all other circumstances you must not

  call this function (I mean it. although in simple tests it might

  actually work, it *will* fail under real world conditions). As a

  special exception, you can also call this method before having

  parsed anything.

  That means you can only use this function to look at or manipulate

  text before or after complete JSON objects, not while the parser

  is in the middle of parsing a JSON object.

  This function is useful in two cases: a) finding the trailing text

  after a JSON object or b) parsing multiple JSON objects separated

  by non-JSON text (such as commas).

 incr_skip

      $json->incr_skip

  This will reset the state of the incremental parser and will

  remove the parsed text from the input buffer so far. This is

  useful after "incr_parse" died, in which case the input buffer and

  incremental parser state is left unchanged, to skip the text

  parsed so far and to reset the parse state.

  The difference to "incr_reset" is that only text until the parse

  error occurred is removed.

 incr_reset

      $json->incr_reset

  This completely resets the incremental parser, that is, after this

  call, it will be as if the parser had never parsed anything.

  This is useful if you want to repeatedly parse JSON objects and

  want to ignore any trailing data, which means you have to reset

  the parser after each successful decode.

MAPPING

  Most of this section is also taken from JSON::XS.

  This section describes how the backend modules map Perl values to

  JSON values and vice versa. These mappings are designed to "do the

  right thing" in most circumstances automatically, preserving

  round-tripping characteristics (what you put in comes out as

  something equivalent).

  For the more enlightened: note that in the following descriptions,

  lowercase *perl* refers to the Perl interpreter, while uppercase

  *Perl* refers to the abstract Perl language itself.

 JSON -> PERL

  object

      A JSON object becomes a reference to a hash in Perl. No

      ordering of object keys is preserved (JSON does not preserver

      object key ordering itself).

  array

      A JSON array becomes a reference to an array in Perl.

  string

      A JSON string becomes a string scalar in Perl - Unicode

      codepoints in JSON are represented by the same codepoints in

      the Perl string, so no manual decoding is necessary.

  number

      A JSON number becomes either an integer, numeric (floating

      point) or string scalar in perl, depending on its range and

      any fractional parts. On the Perl level, there is no

      difference between those as Perl handles all the conversion

      details, but an integer may take slightly less memory and

      might represent more values exactly than floating point

      numbers.

      If the number consists of digits only, this module will try to

      represent it as an integer value. If that fails, it will try

      to represent it as a numeric (floating point) value if that is

      possible without loss of precision. Otherwise it will preserve

      the number as a string value (in which case you lose

      roundtripping ability, as the JSON number will be re-encoded