---
name: "Pandoc::Filter::HeaderIdentifiers"
section: "3pm"
platform: "linux"
package: "libpandoc-elements-perl"
version: "0.38-7"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Pandoc::Filter::HeaderIdentifiers"
---

# Pandoc::Filter::HeaderIdentifiers(3pm)

Add identifiers to headers

## NAME

Pandoc::Filter::HeaderIdentifiers - Add identifiers to headers

## SYNOPSIS

```
  my $id = header_identifier( $header->content );       # calculate identifier
  Pandoc::Filter::HeaderIdentifiers->new->apply($doc);  # add all identifiers
```

## DESCRIPTION

This Pandoc::Filter adds identifier attributes (id) to all Headers elements. It uses the same algorithm as internally used by pandoc.  The module also exports function `"header_identifier"` to calculate an identifier from a list of elements.

## FUNCTIONS

### header\_identifier( $content \[, $ids \] )

Returns an identifier for a given list of inlines or string (`$content`). Optionally takes into account and updates existing ids, given as hash reference mapping identifier to usage count (`$ids`).

## METHODS

### apply( $element \[, $ids \] )

Add identifiers to all Header elements found at a given element (typically a Document. A hash reference of existing identifier counts (or an empty hash to get the new counts) can be passed in addition.

## CHARACTER PROPERTIES

### InPandocHeaderIdentifier

Matches all Unicode lowercase letters, digits 0 to 9, underscore, hyphen, and period. In the unlikely event that you want to check whether a given string could have been generated as header identifier, use this:

```
  $id =~ /^\p{InPandocHeaderIdentifier}+$/ and $id =~ /^\p{Letter}/
```

## SEE ALSO

\<http://pandoc.org/MANUAL.html#header-identifiers\>