#!usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use File::Find::Rule;

sub process_file {
    my %HoH;
    while (<>) {
	chomp;
	my %hash;
	my @data = split /,/, $_; # split each line on comma
	my @keys = ('HOSTNAME', 'IP', 'MAC');
	@hash{@keys} = @data; # hash slice
	$HoH{$ARGV}{$.} = \%hash;
    } continue {
	close ARGV if eof;
    }
    return \%HoH;
}

sub get_xml_files {
    my @dirs = ('.');
    my $level = shift // 2;

    my @files = File::Find::Rule->file()
	->name('*.xml')
	->maxdepth($level)
	->in(@dirs);

    return \@files;
}

print Dumper process_file();
print Dumper get_xml_files();

__END__

$ perl test.pl file2.txt file1.txt
$VAR1 = {
          'file2.txt' => {
                           '3' => {
                                    'HOSTNAME' => 'hostf',
                                    'IP' => '6.6.6.6',
                                    'MAC' => '00000C123458'
                                  },
                           '1' => {
                                    'HOSTNAME' => 'hostd',
                                    'MAC' => '00000C123456',
                                    'IP' => '4.4.4.4'
                                  },
                           '2' => {
                                    'HOSTNAME' => 'hoste',
                                    'MAC' => '00000C123457',
                                    'IP' => '5.5.5.5'
                                  }
                         },
          'file1.txt' => {
                           '1' => {
                                    'IP' => '1.1.1.1',
                                    'MAC' => '00000C123456',
                                    'HOSTNAME' => 'hosta'
                                  },
                           '2' => {
                                    'HOSTNAME' => 'hostb',
                                    'MAC' => '00000C123457',
                                    'IP' => '2.2.2.2'
                                  },
                           '3' => {
                                    'HOSTNAME' => 'hostc',
                                    'MAC' => '00000C123458',
                                    'IP' => '3.3.3.3'
                                  }
                         }
        };
$VAR1 = [
          'response.xml'
        ];