use Email::MIME;

sub handle_parts {
    my $part = shift;
    my $content_type = $part->content_type;
    #print "Content-Type: $content_type\n";  # debug

    my $body = $part->body;
    
    if ($content_type =~ m#text/plain#) {
        return $body;
        
    } elsif ($content_type =~ m#text/html#) {
        return html2text($body);
        
    } elsif ($content_type =~ m#multipart/#) {
        for my $subpart ($part->parts) {
            my $text = handle_parts($subpart);
            return $text if defined $text;
        }
    }
    return;
}

sub html2text {
    my $html = shift;
    # my $text = ...  (left as an exercise)
    # return $text;
    return $html;
}

my $message = ...

my $parsed = Email::MIME->new($message);

my $text = handle_parts($parsed);