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
Before version 2.81 this module had broken both decoder and encoder. It caused that module inserted additional spaces and produced invalid MIME encoded strings. Decoder lot of times discarded white space characters, incorrectly interpreted data or decoded Base64 string as Quoted-Printable.
As of version 2.81 encoder should be fully compliant of RFC 2047. Due to bugs in previous versions decoder is less strict and allows to decode also incorrectly encoded strings by previous versions of this module. But decoded strings will be slightly different.
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
RFC 2047, http://www.faqs.org/rfcs/rfc2047.html and many other locations.