Well, taken from the ActivePerl site;
Visual Perl is the high-productivity Perl plug-in for Visual Studio .NET. Powerful, Perl-specific features within the familiar Visual Studio environment provide ease of use and accelerated development cycles.
Visual Perl integrates seamlessly with Visual Studio .NET, allowing programmers to fully leverage the features of Microsoft's popular development tool suite.
It really just allows one to use the Visual Studio.net IDE for programming Perl. I used the beta, and thought it was ok, but to be honest my PC is kinda slow (Cyrix 300) and lacking on ram, so I didn't really get to grips with it that much. It offered a lot of functionallity, and is probably nice if you're gonna code Perl along side one of the .Net languages.
It's not really a 'platform' as such, as an editor, like Emacs or VIM. As for your other queries: You can use as many perl modules as you like (although ActivePerl users generally use PPM and not CPAN). And it isn't just for web programming, you can code whatever you like, I don't know what gave you the impression that it was aimed specifically at web development.
So, to some up - it's just an IDE. If you like Visual Studio, and don't mind the price, go for it. If you prefer ViM or Emacs, then don't go for it :). I myself kinda like ViM, but do almost all of my web programming in Editplus
, mainly because all the unix desktops are too slow to be usable on this PC.
To be honest, I find the PerlNet component in the Perl Development Kit to be much more interesting. That allows one to use Perl as a .Net language, in much the same way that Jython allows one to write Java bytecode in Jython.