#!/usr/bin/perl --
use strict;
use warnings;
use XML::LibXML 1.70; ## for load_html/load_xml/location

my $xml = q{<contrib-group>
  <contrib contrib-type="author">
.
some code
.
<x>, </x></contrib>
  <contrib contrib-type="author">
.
some code
.
<x>, </x></contrib>
  <contrib contrib-type="author">
.
some code
.
<x> and </x></contrib>
  <contrib contrib-type="author">
.
some code
.
</contrib>
</contrib-group>
};

my $dom = XML::LibXML->new(qw/ recover 2 /)->load_xml(
#~     location => $filepath_or_http,
    string => $xml,
);

print $dom->find(q{   //contrib/x[ contains( . , ' and ' ) ]      })->shift->nodePath, "\n";

if( my $cx = $dom->findnodes(q{    //contrib/x    })->pop ){
    print $cx->nodePath, "\n";
    print "$cx\n";
    my $tx = $cx->textContent;
    $tx =~ s/ and / , /;
    $cx->removeChildNodes;
    $cx->appendText( $tx ); 
    print "$cx\n\n\n";
}

print "$dom\n";
__END__
/contrib-group/contrib[3]/x
/contrib-group/contrib[3]/x
<x> and </x>
<x> , </x>