use XML::Simple;
use Hash::Merge;

my %config1 = %{XMLin ('file1')};
my %config2 = %{XMLin ('file2')};
my %newhash;
Hash::Merge::set_behavior ('RIGHT_PRECEDENT');
*newhash = merge (\%config1, \%config2);
XMLout (\%newhash, outputfile => "newfile", xmldecl => 1, rootname => 'config');