#!/usr/bin/perl

use 5.010;
use strict;
use warnings;

use XML::LibXML;

my $new_values_file = shift;
open my $in, '<', $new_values_file or die "$new_values_file: $!";
chomp(my @new_values = <$in>);

my $dom = 'XML::LibXML'->load_xml(IO => *STDIN);

my $i = 0;
foreach my $alt_trans ($dom->findnodes('//file/body/group/unit/alt-title/otherTitle[@origin="title"]')) {
    print $alt_trans->to_literal();
    $alt_trans->removeChildNodes if $alt_trans->findnodes('text()');
    $alt_trans->appendText($new_values[$i]);
    $i++;
}

##</code><code>##

...
<group>
 <unit id="3Ojs1SLwMmEHK8mJ0_dc2:43”>
  <titleEN>{3&gt;19&lt;3}</ titleEN >
  <titleFR>{3&gt;19&lt;3}</ titleFR >
  <alt-title origin="tilte"><otherTitle/></ alt-title>
  <alt-title origin="price"><otherPrice/></ alt-title>
 </unit>
</group>
<group>
 <unit id="3Ojs1SLwMmEHK8mJ0_dc2:43”>
  <titleEN>{3&gt;19&lt;3}</ titleEN >
  <titleFR>{3&gt;19&lt;3}</ titleFR >
  <alt-title origin="tilte"><otherTitle/></ alt-title>
  <alt-title origin="price"><otherPrice/></ alt-title>
 </unit>
</group>
...