Just use the Encode module that comes with Perl. It does the RFC 2047 decoding in one step: 

use Encode;

my $russkiy = decode("mime-header", "=?UTF-8?B?0KDRg9GB0YHQutC40Lk=?="
+);

[download]
$russkiy is a proper 7 character Perl unicode string.

Juerd # { site => 'juerd.nl', do_not_use => 'spamtrap', perl6_server => 'feather' }

PS- You can use Russian variable names too, if you wish: 

use utf8;
use Encode;

my $русский = ...;
PPS- Perl Monks sucks for not allowing Unicode characters in <code>-blocks.

In reply to Re: reading Base64 encoded Unicode email returns mangled text by Juerd
in thread reading Base64 encoded Unicode email returns mangled text by Errto

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