use File::Find;

find(\&wanted, 'y:\health\biru');

sub wanted {
	if ($_ ne "." && lc() ne $_) {
		print("Renaming $_ to " . lc() . "\n");
		rename($_, lc()  . "_______") or die("failed: $!");
		rename(lc() . "_______", lc()) or die("failed: $!");
	}
	
	if (/\.html$/) {
         //change any href="XXX" or src="XXX" to href="xxx" etc.
...