Merge branch 'ab/send-email-perl' into next

Merge branch 'ab/send-email-perl' into next

* ab/send-email-perl:
  send-email: extract_valid_address use qr// regexes
  send-email: is_rfc2047_quoted use qr// regexes
  send-email: use Perl idioms in while loop
  send-email: make_message_id use "require" instead of "use"
  send-email: send_message die on $!, not $?
  send-email: use (?:) instead of () if no match variables are needed
  send-email: sanitize_address use qq["foo"], not "\"foo\""
  send-email: sanitize_address use $foo, not "$foo"
  send-email: use \E***\Q instead of \*\*\*
  send-email: cleanup_compose_files doesn't need a prototype
  send-email: unique_email_list doesn't need a prototype
  send-email: file_declares_8bit_cte doesn't need a prototype
  send-email: get_patch_subject doesn't need a prototype
  send-email: use lexical filehandles during sending
  send-email: use lexical filehandles for $compose
  send-email: use lexical filehandle for opendir