Pandoc::Metadata - pandoc document metadata


Document metadata such as author, title, and date can be embedded in different documents formats. Metadata can be provided in Pandoc markdown format with metadata blocks at the top of a markdown file or in YAML format like this:

  title: a title
    - first author
    - second author
  published: true

Pandoc supports document metadata build of strings ("MetaString"), boolean values ("MetaBool"), lists ("MetaList"), key-value maps ("MetaMap"), lists of inline elements ("MetaInlines") and lists of block elements ("MetaBlocks"). Simple strings and boolean values can also be specified via pandoc command line option -M or --metadata:

  pandoc -M key=string
  pandoc -M key=false
  pandoc -M key=true
  pandoc -M key

Perl module Pandoc::Elements exports functions to construct metadata elements in the internal document model and the general helper function metadata.


All Metadata Elements support common element methods (name, to_json, string, ...) and return true for method is_meta.

value( [ $key | $pointer ] [ %options ] )

Called without an argument this method returns an unblessed deep copy of the metadata element. Plain keys at the root level (unless they start with /) and JSON Pointer expressions (RFC 6901) can be used to select subfields. Note that JSON Pointer escapes slash as ~1 and character ~ as ~0. URI Fragment syntax is not supported.

  $doc->value;                   # full metadata
  $doc->value("");               # full metadata, explicitly
  $doc->value('/author');        # author field
  $doc->value('author');         # author field, plain key
  $doc->value('/author/name');   # name subfield of author field
  $doc->value('/author/0');      # first author field
  $doc->value('/author/0/name'); # name subfield of first author field
  $doc->value('/~1~0');          # metadata field '/~'
  $doc->value('/');              # field with empty string as key

Returns undef if the selected field does not exist.

As a debugging aid you can set option strict to a true value. In this case the method will croak if an invalid pointer, invalid array index, non-existing key or non-existing array index is encountered.

Instances of MetaInlines and MetaBlocks are stringified by unless option element is set to keep.

Setting option boolean to JSON::PP will return JSON::PP:true or JSON::PP::false for MetaBool instances.



A plain text string metadata value.

    MetaString $string
    metadata "$string"


A Boolean metadata value. The special values "false" and "FALSE" are recognized as false in addition to normal false values (0, undef, "", ...).

    MetaBool $value
    metadata JSON::true()
    metadata JSON::false()


A list of other metadata elements.

    MetaList [ @values ]
    metadata [ @values ]


A map of keys to other metadata elements.

    MetaMap { %map }
    metadata { %map }


Container for a list of inlines in metadata.

    MetaInlines [ @inlines ]


Container for a list of blocks in metadata.

    MetaBlocks [ @blocks ]

The string method concatenates all stringified content blocks separated by empty lines.