hosts.csv data:
R17N6340-C04-1;10.1.70.1
R17N6340-C04-2,10.1.70.2
R17N6340-C04-3,10.1.70.3

#!/usr/bin/perl
#use strict;
#use warnings;
my $xml_file  = 'template.txt';
my $list_file = 'hosts.csv';
my $out_file  = 'newhost.xml';
#
open( XML,  '<:utf8', $xml_file  );
open( LIST, '<:utf8', $list_file );
open( OUT,  '>>:utf8', $out_file  );

my $xml;
{ local $/ = undef; $xml = <XML>; };

my $line;
foreach $line ( <LIST> ) {
    # Skipping if the line is empty or a comment
    next if  $line =~ /^\s*$/ ;
    next if  $line =~ /^\s*#/ ;
    my ($hostname, $interface) = split(/,/, $lin);
    $xml =~ s/hostname/$hostname/g;
    $xml =~ s/interface/$interface/g;
}
print XML $xml;

close