Mail::Box Removing $& performance issue

$& causes global performance issues for any program that includes use of 
that variable, even if the code is never executed.

Mail::Message::Head::Complete.pm uses $& on line 514 and can be changed to

my $sender = $from =~ m/(\<.*?\>)/ ? $1 : 'unknown';

Mail::Message::/TransferEnc::Sevenbit.pm line 37 has another instance, 
though I wasn't able to test a change.

The IMAP Client code has numerous instances, but those are much less 
important

Thanks,
    Todd Richmond