my @emails = (
  'To: <firstone@somewhere.com>',
  'To: You and I <secondone@somewhere.com>',
  'To: thirdone@somewhere.com'
);

for (@emails) {
  /^To:\s*[^<]*<([^>]+)>/ || /^To:\s*(.+)$/;
  print $1, $/;
}