Encode::MIME::Header(3p)

NAME
Encode::MIME::Header -- MIME 'B' and 'Q' header encoding

SYNOPSIS
    use Encode qw/encode decode/;
    $utf8   = decode('MIME-Header', $header);
    $header = encode('MIME-Header', $utf8);

ABSTRACT
This module implements RFC 2047 Mime Header Encoding. There are 3 variant encoding names; "MIME-Header", "MIME-B" and "MIME-Q". The difference is described below

              decode()          encode()
  ----------------------------------------------
  MIME-Header Both B and Q      =?UTF-8?B?....?=
  MIME-B      B only; Q croaks  =?UTF-8?B?....?=
  MIME-Q      Q only; B croaks  =?UTF-8?Q?....?=

DESCRIPTION
When you decode(=?encoding?X?ENCODED WORD?=), ENCODED WORD is extracted and decoded for X encoding (B for Base64, Q for Quoted-Printable). Then the decoded chunk is fed to decode(encoding). So long as encoding is supported by Encode, any source encoding is fine.

When you encode, it just encodes UTF-8 string with X encoding then quoted with =?UTF-8?X?....?= . The parts that RFC 2047 forbids to encode are left as is and long lines are folded within 76 bytes per line.

BUGS
It would be nice to support encoding to non-UTF8, such as =?ISO-2022-JP? and =?ISO-8859-1?= but that makes the implementation too complicated. These days major mail agents all support =?UTF-8? so I think it is just good enough.

Due to popular demand, 'MIME-Header-ISO_2022_JP' was introduced by Makamaka. Thre are still too many MUAs especially cellular phone handsets which does not grok UTF-8.

SEE ALSO
Encode

RFC 2047, <http://www.faqs.org/rfcs/rfc2047.html> and many other locations.