Welcome to Perl and to the monastery Arenas,

powershell is not a programming language, so you probably can profit from some basic reading about Perl as the book Beginning Perl or the (old but still usefull) Perl Cookbook.
Some sparse suggestion being you new to Perl and using winz: you can check if you have a Perl's module installed with a simple oneliner (take a look at perldoc about command line switches)

perl -MNot::Installed::Module -e "1"
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You are executing (-e) an always-return-true mini Perl program (what is inside the doublequote) but loading some module (after the -M ) before runnig the code. You obviosly get:

Can't locate Not/Installed/Module.pm in @INC (@INC contains:...
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You can install modules using the cpanp client (working in the strawberry Perl distro on which DWimPerl is built)

cpanp -i Not::Installed::Module
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Choose carefully module to install and use: XML::Simple is simply deprecated. Other modules are better but you need to learn how to use them: the following, working, code uses XML::Twig for xml parsing: anyway, even if you use a good module, xml parsing is a little triky and shaggy thing.

#!perl
use strict;
use warnings;

use XML::Twig;
my $t= XML::Twig->new(pretty_print => 'indented',
                    twig_handlers => {
                          'city/name'=>sub{  print $_[1]->text,"\n"; }
+,
                          'city/population'=>sub{  print "Pop: ",$_[1]
+->text,"\n"; },
                    }
);

$t->parseurl('http://athome.myminicity.com/xml');

__OUTPUT__
AtHome
        Pop: 18998557
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As last suggestion, when asking here at perlmonks, do your best to present a simple and fully understandable question, with code that reproduce the error you are facing, or being clear about data you have and data you want to get back from your program. Asking clear question let you to have in return good answers, sometimes real gems, lurking here very wise and experienced programmers (not me).

htH
L*