大崎さんのperlメモを拝見させていただいたのですが、
下記のようでよいのでしょうか？
$mail_regex =
q{(?:[^(\040)<>@,;:".\\\\\[\]\000-\037\x80-\xff]+(?![^(\040)<>@,;:".\\\\} .
q{\[\]\000-\037\x80-\xff])|"[^\\\\\x80-\xff\n\015"]*(?:\\\\[^\x80-\xff][} .
q{^\\\\\x80-\xff\n\015"]*)*")(?:\.(?:[^(\040)<>@,;:".\\\\\[\]\000-\037\x} .
q{80-\xff]+(?![^(\040)<>@,;:".\\\\\[\]\000-\037\x80-\xff])|"[^\\\\\x80-} .
q{\xff\n\015"]*(?:\\\\[^\x80-\xff][^\\\\\x80-\xff\n\015"]*)*"))*@(?:[^(} .
q{\040)<>@,;:".\\\\\[\]\000-\037\x80-\xff]+(?![^(\040)<>@,;:".\\\\\[\]\0} .
q{00-\037\x80-\xff])|\[(?:[^\\\\\x80-\xff\n\015\[\]]|\\\\[^\x80-\xff])*} .
q{\])(?:\.(?:[^(\040)<>@,;:".\\\\\[\]\000-\037\x80-\xff]+(?![^(\040)<>@,} .
q{;:".\\\\\[\]\000-\037\x80-\xff])|\[(?:[^\\\\\x80-\xff\n\015\[\]]|\\\\[} .
q{^\x80-\xff])*\]))*};
$hoge = 'From: =?ISO-2022-JP?B?xxxxxxxxxxxxx=?= <xxxxx@xxxxxxx.xxx>';
$hoge =~ s/^From: .*?($mail_regex).*$/$mail=$1/e;