use MIME::Base64;

open my $reader, "TEST.gif";

while (read($reader, $buffer, 10*57)) {
   $file_data .= decode_base64(encode_base64($buffer, ''))
}

open my $writer, ">TEST_base64.gif";
print $writer $file_data;

__END__

`dir` output:
11/24/2005  03:13 AM            66,072 TEST.gif
04/16/2006  09:28 PM            66,437 TEST_base64.gif

##</code><code>##

This is perl, v5.8.8 built for MSWin32-x86-multi-thread
(with 25 registered patches, see perl -V for more detail)