---
name: "HTTP::Headers::Util"
section: "3pm"
platform: "linux"
package: "perl-http-message"
version: "7.04-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/HTTP::Headers::Util"
---

# HTTP::Headers::Util(3pm)

## SYNOPSIS

```
  use HTTP::Headers::Util qw(split_header_words);
  @values = split_header_words($h->header("Content-Type"));
```

## DESCRIPTION

This module provides a few functions that helps parsing and construction of valid HTTP header values.  None of the functions are exported by default.

The following functions are available:

- split\_header\_words( @header\_values )

  This function will parse the header values given as argument into a list of anonymous arrays containing key/value pairs.  The function knows how to deal with ",", ";" and "=" as well as quoted values after "=".  A list of space separated tokens are parsed as if they were separated by ";".

  If the `@header_values` passed as argument contains multiple values, then they are treated as if they were a single value separated by comma ",".

  This means that this function is useful for parsing header fields that follow this syntax (BNF as from the HTTP/1.1 specification, but we relax the requirement for tokens).

  ```
    headers           = #header
    header            = (token | parameter) *( [";"] (token | parameter))
    token             = 1*<any CHAR except CTLs or separators>
    separators        = "(" | ")" | "<" | ">" | "@"
                      | "," | ";" | ":" | "\" | <">
                      | "/" | "[" | "]" | "?" | "="
                      | "{" | "}" | SP | HT
    quoted-string     = ( <"> *(qdtext | quoted-pair ) <"> )
    qdtext            = <any TEXT except <">>
    quoted-pair       = "\" CHAR
    parameter         = attribute "=" value
    attribute         = token
    value             = token | quoted-string
  ```

  Each *header* is represented by an anonymous array of key/value pairs.  The keys will be all be forced to lower case. The value for a simple token (not part of a parameter) is `"undef"`. Syntactically incorrect headers will not necessarily be parsed as you would want.

  This is easier to describe with some examples:

  ```
     split_header_words('foo="bar"; port="80,81"; DISCARD, BAR=baz');
     split_header_words('text/html; charset="iso-8859-1"');
     split_header_words('Basic realm="\\"foo\\\\bar\\""');
  ```

  will return

  ```
     [foo=>'bar', port=>'80,81', discard=> undef], [bar=>'baz' ]
     ['text/html' => undef, charset => 'iso-8859-1']
     [basic => undef, realm => "\"foo\\bar\""]
  ```

  If you don't want the function to convert tokens and attribute keys to lower case you can call it as `"_split_header_words"` instead (with a leading underscore).

- join\_header\_words( @arrays )

  This will do the opposite of the conversion done by **split\_header\_words()**. It takes a list of anonymous arrays as arguments (or a list of key/value pairs) and produces a single header value.  Attribute values are quoted if needed.

  Example:

  ```
     join_header_words(["text/plain" => undef, charset => "iso-8859/1"]);
     join_header_words("text/plain" => undef, charset => "iso-8859/1");
  ```

  will both return the string:

  ```
     text/plain; charset="iso-8859/1"
  ```