The XML Declaration (Perl and XML)

2.7. The XML Declaration

After reading about character encodings, an astute reader may wonder how to declare the encoding in the document so an XML processor knows which one you're using. The answer is: declare the decoding in the XML declaration. The XML declaration is a line at the very top of a document that describes the kind of markup you're using, including XML version, character encoding, and whether the document requires an external subset of the DTD. The declaration looks like this:

<?xml version="1.0" encoding="utf8" standalone="yes"?>

The declaration is optional, as are each of its parameters (except for the required version attribute). The encoding parameter is important only if you use a character encoding other than UTF-8 (since it's the default encoding). If explicitly set to "yes", the standalone declaration causes a validating parser to raise an error if the document references external entities.