XPath

XPath is an XML-related technology (but not notated in XML) that allows one to locate nodes in XML files using a compact syntax. One can use it using XML::LibXML, and should avoid using the old, slow, and largely unmaintained XML::XPath CPAN distribution.

Another useful module is HTML-Selector-XPath which allows one to convert CSS-style selectors to XPath and provides functionality similar to that offered by such JavaScript libraries such as jQuery. So you can, for example, write selector_to_xpath('ul.myclass a') to find all a elements inside a ul element with a CSS class of myclass.

To learn about XPath, consult the following resources:

• Zvon XPath Tutorial

• Zvon XPath Reference

• Interactive XPath tester

XSLT

XSLT stands for Extensible Stylesheet Language Transformations and is a language for transforming XML documents into other XML documents or other formats such as HTML or plain text. Perl has good support for version 1.0 of XSLT by using the XML-LibXSLT distribution.

(Please avoid using XML-XSLT which is old, and largely unmaintained. Use XML-LibXSLT instead.)

For more about XSLT, see the following links, but note that XSLT makes extensive use of XPath, so you should learn it first.

• The Zvon XSLT Tutorial - with many examples.

• The Zvon XSLT Reference - provides a useful reference.

• Interactive XSLT tester - it seems that the best results are achieved with the Mozilla Firefox browser, because Google Chromium/Google Chrome and Opera do not handle XML namespaces with XSLT well.

XML-Simple

XML-Simple is not so simple when done properly and takes the wrong approach to dealing with XML. Please avoid using it. Look at XML-LibXML for an easy and fast alternative.

Parsing XML Using Regular Expressions

You should also avoid parsing XML using regular expressions, because it is difficult to handle the non-regular grammar of XML using them. Instead, use a parser. For more information see:

1. “Parsing HTML the Cthulhu Way”.

2. Comment on Stack Overflow (funny).