use strict;
use warnings;
use XML::LibXML;

print "Please specify node c content\n";
my $node_c = <STDIN>;
chomp $node_c;

my $template = "xx.xml";
my $parser = XML::LibXML->new();
my $doc = $parser->parse_file($template);
my($object0) = $doc->findnodes("/header/id/c/text()");
my $text0 = XML::LibXML::Text->new($node_c);
$object0->replaceNode($text0);