use strict;
use warnings;
use XML::Twig;

my %ok_cities;
my $twig= XML::Twig->new(pretty_print => 'indented',
   twig_handlers=>{
                    '/cities/City/StreetList/Street'=>sub{
                     if ($_[1]->att('bars')!~/none/){
                       push @{$ok_cities{$_[1]->parent()->parent()->att('name')}},
                            $_[1]->att('name');
                      }
                     }
   }
);
$/='';
$twig->parse(<DATA>);
print map {"In '$_' these streets have bars: ".
           (join',',@{$ok_cities{$_}}).
           "\n"} sort keys %ok_cities;

__DATA__
<?xml version="1.0" encoding="UTF-8"?>
<cities>
<City name="Some City">
    <Properties location="SomeCountry"/>
    <StreetList version="1">
        <Street name="Foo Street" bars="none"/>
        <Street name="Bar Street" bars="plenty"/>
    </StreetList>
</City>
<City name="Other City">
    <Properties location="Narnia"/>
    <StreetList version="5">
        <Street name="Lovely Street" bars="some"/>
        <Street name="Gray Street" bars="none"/>
    </StreetList>
</City>
</cities>