Encode::MIME::Header 2.23

Encode::MIME::Header is a Perl module that contains 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?....?=

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.