use warnings;
use strict;
use XML::Twig;
my $source_file = 'datafile_towns.xml';
my $out_file = 'illytowns.xml';
my $twig = XML::Twig->new(
    twig_handlers => { town => \&town },
);

$twig->parsefile($source_file);
open (my $fh_out, '>', $out_file) or die "unable to open '$out_file' for writing: $!";

sub town {
    my ($twig, $town) = @_;
    my $townx = $town->first_child('location')->first_child('mapx')->text;
    my $towny = $town->first_child('location')->first_child('mapy')->text;
    if (($townx > 556) and ($towny > -2502) and ($towny < -2214)) {
        print $town->first_child('towndata')->first_child_text('townname');
        print "\n";
    }
    
    $twig->print($fh_out);
    $twig->purge;
}