How can I search and replace XML based on values in a Perl hash?

Question

I have an XML file in a string variable ($data), and a hash containing all the tag names and their contents (%field_list).

The tag names are to be checked so that if they are enumerated fields, their contents should be replaced with strings.

Does anybody know if it is possible to do this with search and replace? I am not having much luck at the moment.

foreach my $field (sort keys %field_list)
{ 
    my $value = $field_list{$field};
    # will return a non-empty string if field is enumerated and value is valid
    my $enum_string = &convert_enumeration_to_string($field, $value);
    if ($enum_string ne "")
    {
#syntax error
$data =~ s/<($field)>($value)</($field)>/<($field)>($enum_string)</($field)>/g;
    }
} 

Does anybody know whether there is anything I can do, or do I need a completely different approach?

Answer 1

Escape your slashes:

$data =~ s/<($field)>($value)<\/($field)>/<($field)>($enum_string)<\/($field)>/g;

Or use different deliminators:

$data =~ s{<($field)>($value)</($field)>}{<($field)>($enum_string)</($field)>}g;

Answer 2

The correct way to do it is:

$data =~ s/<($field)>($value)<\/($field)>/<$field>$enum_string<\/$field>/g;

Answer 3

Well, let's jump into the XML bandwagon: use an XML library like XML::LibXML to manipulate XML documents.

use XML::LibXML;
my $dom = XML::LibXML->load_xml(string => $data);

foreach my $field (sort keys %field_list) {
    my $value = $field_list{$field};
    if (my $enum_string = &convert_enumeration_to_string($field, $value)) {
        foreach my $node ($dom->findnodes("//xml/${field}[. = '$value']")
            ->get_nodelist) {
            my $element = $dom->createElement($field);
            $element->appendText($enum_string);
            $node->replaceNode($element);
        }
    }
}

print $dom->toString;