#!/usr/lib/perl
use strict;
use warnings;
use Carp;
use File::Find;
use File::Spec::Functions qw( canonpath );

if ( @ARGV == 0 ) {
    push @ARGV, "C:/file/dir";
    warn "Using default path $ARGV[0]\n  Usage: $0  path ...\n";
}

# open an output file whose name won't be found by File::Find
open( my $allxml, '>', "all_xml_contents.combined" )
    or die "can't open output xml file for writing: $!\n";
print $allxml '<?xml version="1.0" encoding="UTF-8"?>', "\n<all_xml_contents>\n";

find(
    sub {
        return unless ( /[.]xml\z/i and -f );
        extract_information();
        return;
    },
    @ARGV
);

print $allxml "</all_xml_contents>\n";

sub extract_information {
    my $path = $_;

    if ( open my $xmlin, '<', $path ) {
        local $_ = <$xmlin>;
        print $allxml $_ unless ( /<\?xml/ );
        while ( <$xmlin> ) {
            print $allxml $_;
        }
    }
    return;
}