Matching email addresses is difficult. But you're not actually trying to validate them, so you can probably afford to just "do your best", as it were :). This is the regexp used in Pod::HTML for matching email addresses; it's not going to catch everything, and it's probably going to wrongly match some addresses. But it may help.

    if ($word =~ /[\w.-]+\@\w+\.\w/) {
        # looks like an e-mail address
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This is used on an individual "word", where a word is obtained by splitting a string on /\s+/. So that's one example. If you look around a bit more, you can probably find others.

For part 2 (sending the email)--if you're sending the same content to each of the addresses, then you could perhaps use Bcc to write all of the addresses to the message.

    for my $addr (@mail_to) {
        print SENDMAIL "Bcc: $addr\n";
    }

    print SENDMAIL "From: csorensen\@uptimeresources.net \n";
    print SENDMAIL "Subject: South African tourism survey \n";
    print SENDMAIL "Content-type: text/plain \n\n";
    print SENDMAIL $content;
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