Your questions cover a very wide range of concerns, from basic Perl syntax to some quite complex issues of the interface between perl and Windows/Office. While I have used Win32::OLE, I have never used it to access office documents, so I can't give you much advice on your primary objective.
It will serve you well to study an introduction to Perl programming, to learn basic syntax, data structures, etc. This will help you with questions like "What does those "::" and "->" in code above stands for ?", "why curly braces ?", etc. There are some excellent tutorials and references in Getting Started with Perl. It will be difficult for you to understand the code you see and reliably deal with objects, variants (Win32::OLE::Variant) and data structures until you have learned the basics.
While I found much of the documentation available on MSDN difficult to unhelpful, the script examples I found very helpful. When I was doing it regularly, I was able to translate VBScript examples to Perl quite reliably. And the MSDN docs did at least identify many of the methods and attributes of the COM objects. My usual route to success was to hunt through MSDN for objects, methods and attributes that looked interesting, then google for examples of them being used to see how they worked.