rename($_, lc($_)) foreach <*.HTM{,L}>;   # yes, this is portable

##</code><code>##

$op = shift or die "Usage: rename expr [files]\n";
chomp(@ARGV = <STDIN>) unless @ARGV;

for (@ARGV) {
   $was = $_;
   eval $op;
   die if $@;
   rename($was, $_) unless $was eq $_;
}

##</code><code>##

rename '$_ = lc' *.HTM *.HTML