1) That seems rather redundant, because you can call the batch-file directly. But you might want to do some processing, so

use strict;
use warnings;

#do something with @ARGV
@ARGV = map { lc($_) } @ARGV;

system (@ARGV);
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2) The WSH can run other languages, like VBScript or JScript. And you can run PerlScript-scripts, that gives you some nice things to play with. Like calling methods written in VBScript from perl and the other way around.
Check the msdn-website. and Active State.

Notes about PerlScript:
- All PerlScript-COM calls are magically done by Win32::OLE, so there is no speed gain when you write "automating scripts" in PerlScript instead of perl.
-PerlScripts run under eval();, so you can run into trouble with some modules that use INIT{}, that can be overcome.