I've found on several occasions that it's necessary to manually upgrade form input to utf8. For some reason, CGI returns raw byte strings, and those might end up being upgraded to utf once more, resulting in lots of squiggly characters. I did this like so:

    use Encode;
    my $email_body = $cgi->param( 'email_body' );
    $email_body    = decode_utf8( $email_body );
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