I'm seeing a 9% improvement in caseless compare over character class.

#!/usr/bin/perl
use Benchmark qw(cmpthese);

my @samples = (
  'this is a test',
  'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa',
  '_______________T________',
  '_______________t________');

cmpthese -1 => {
        class    => 'grep (/[Tt]/, @samples)',
        caseless => 'grep (/t/i,   @samples)'};



              Rate    class caseless
class    2299509/s       --      -8%
caseless 2502283/s       9%       --
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