For the better part of this past year, I've been the principal engineer at my company on a project involving handling XML data.  I chose to use XML::Simple (with XML::LibXML::SAX for the parser), and it has served my needs quite well, even though it was my first real experience with XML processing.

Along the way, I've needed to massage input text so that XML::Simple would handle it correctly.  The XML is always output as "UTF-8", and the subroutine I was using for "cleaning" the input text looked like this:

sub xml_compliance {
    my ($self, $field) = @_;
    $field =~ s/&/&/g;
    $field =~ s/</&lt;/g;
    $field =~ s/>/&gt;/g;
    $field =~ s/"/&quot;/g;
    $field =~ s/'/&#39;/g;
    return $field;
}
[download]

Yesterday we discovered that this wasn't sufficient; an error occurred because someone gave us input containing a character which looked like an apostrophe (ascii 0x27), but was in fact an ascii 0x92 ("smart quotes", or whatever they're called), which broke the parsing.  When I say "broke the parsing", I mean that I this error from XMLin:

    Entity: line 15: parser error : Input is not proper UTF-8, indicat
+e encoding !
[download]

So I revised my subroutine as follows:

sub xml_compliance {
    my ($self, $field) = @_;

    my $fixed = "";

    my $h_translate = {
        '&' => '&',
        '<' => '&lt;',
        '>' => '&gt;',
        '"' => '&quot;',
        "'" => '&#39;',
    };

    my @chars = split //, $field;
    foreach my $char (@chars) {
        if (exists $h_translate->{$char}) {
            $fixed .= $h_translate->{$char};
        } elsif (ord($char) > 0x7f) {
            # This is where we handle all non 7-bit ascii
            $fixed .= sprintf "&#%02x;", ord($char);
        } else {
            $fixed .= $char;
        }
    }

    return $fixed;
}
[download]

That is, it will handle those "smart quotes" by converting them to "\", as well as any other ascii characters with the high bit turned on.

My questions are:

1. Is this an appropriate way to handle such characters?
2. Is there some simpler/easier/better way to do it?
3. Is there some module for this which I'm unaware of?
4. Is there anything else I should be taking into account?

Thanks in advance for any enlightenment!