Example:
   my %myhash = ();
   my $key1 = "MixedCase";
   my $lower_key1 = lc($key1);
   $myhash{$lower_key1} = "Some Value";
   if (exists($myhash{lc("MIXEDCASE")})) {
      print "YES it exists!\n";
   }
   else {
      print "NO it doesn't exist!\n";
   }