use Cwd; # module for finding the current working directory
$|=1;    # turn off I/O buffering

# 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;
    print "Work dir = $workdir\n";
    my ($startdir) = &cwd; # keep track of where we began

    chdir($workdir) or die "Unable to enter dir $workdir:$!\n";
    opendir(DIR, ".") 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 "..");

        if (-d $name){                  # is this a directory?
            &ScanDirectory($name);
            next;
        }
        else {          # this is a file
            print "Name = $name\n";
            $newName = $name;
            $newName =~ s/\..*//;
            $newName .= ".xml";
            $result = rename($name, $newName) 
or die "cannot rename $name to $newName:$!";
        }
        chdir($startdir) or 
die "Unable to change to dir $startdir:$!\n";
    }
}
&ScanDirectory($ARGV[0]);