use File::Spec::Functions qw( catfile );

# This subroutine takes the name of a directory and recursively scans
# down the filesystem from that point looking for files named "core"
sub ScanDirectory{
    my $workdir = shift;
    if ($workdir =~ /^[a-zA-Z]:\z/) {
       $workdir .= '.';   # Fix bug in Windows.
    }

    print "Work dir = $workdir\n";

    opendir(local *DIR, $workdir)
        or die "Unable to open $workdir: $!\n";
    my @names = readdir(DIR)
        or die "Unable to read $workdir: $!\n";
    closedir(DIR);

    foreach my $name (@names){
        next if ($name eq ".");
        next if ($name eq "..");
        my $fqname = catfile($workdir, $name);

        if (-d $fqname){                  # is this a directory?
            ScanDirectory($fqname);
            next;
        }

        print "Name = $name\n";
        $newName = $name;
        $newName =~ s/\..*//;
        $newName .= ".xml";
        my $new_fqname = catfile($workdir, $newName);
        $result = rename($fqname, $new_fqname) 
            or die "Cannot rename $fqname to $new_fqame: $!"\n;
    }
}

$|=1;    # Turn off I/O buffering
ScanDirectory($ARGV[0]);