bug: decode RFC 2047 headers for Email::MIME address parsing #1141

Summary

The CPAN compatibility run 20260826-133502-83100 fails Email::MIME 1.954 while processing RFC 2047 encoded headers and encoded display names. The same failures reproduce on both the JVM and interpreter backends.

Email::MIME is pure Perl. Its upstream test suite passes completely under system Perl 5.42.2 when run with the distribution's required dependencies in an isolated library.

Upstream baseline

System Perl passes the complete Email::MIME 1.954 suite:

Files=21, Tests=297
Result: PASS

PerlOnJava failures

Encoded headers are not decoded

t/unicode.t fails 30 of 59 assertions on both backends. For example, a UTF-8 encoded-word display name remains encoded instead of decoding:

got:      =?UTF-8?B?RMO2eQ==?= <test@example.com>
expected: Døy <test@example.com>

Long encoded subjects are similarly returned as RFC 2047 encoded words rather than decoded text.

Address-list parsing fails after encoded words

t/header-addresslist.t fails while parsing encoded display names and group addresses, then dies while accessing an expected parsed address object:

Can't call method "phrase" on an undefined value at t/header-addresslist.t line 58.

For example, an encoded address header is returned as encoded words rather than as the decoded quoted phrases expected by the test.

Reproduction

From an unpacked Email::MIME 1.954 distribution, after building its blib directory and making its normal prerequisites available:

jperl -Iblib/lib -It t/unicode.t
jperl -Iblib/lib -It t/header-addresslist.t

jperl --interpreter -Iblib/lib -It t/unicode.t
jperl --interpreter -Iblib/lib -It t/header-addresslist.t

Observed results on both backends:

t/unicode.t:            30/59 failed
t/header-addresslist.t: fails assertions 3-4, 6, 8-9, 11, 13-14, 16-18; exits when calling phrase on undef

Expected behavior

RFC 2047 encoded words must be decoded before the values are exposed through Email::MIME's header and address-list APIs. Encoded display names and group-address syntax must then parse into the same values and address objects as system Perl.

Likely scope

The common behavior across these tests suggests a compatibility gap in encoded-word handling at the Email::MIME / Email::Simple header boundary, with the address-list failures as a downstream consequence. Both execution backends are affected, so the issue is likely shared runtime or bundled-module behavior rather than JVM-only compilation.