use Benchmark 'timethese';

sub eq_alone    { $_[0] eq 'cr' || $_[0] eq 'CR'; }
sub lc_eq       { lc($_[0]) eq 'cr'; }
sub regex       { $_[0] =~ /^cr$/i; }

timethese (2_000_000, {
        eq_alone => sub { eq_alone('cr'); eq_alone('CR'); },
        lc_eq    => sub { lc_eq('cr');    lc_eq('CR');    },
        regex    => sub { regex('cr');    regex('CR');    },
});

__END__

Benchmark: timing 2000000 iterations of eq_alone, lc_eq, regex...
  eq_alone: 22 secs (21.48 usr  0.00 sys = 21.48 cpu)
     lc_eq: 22 secs (22.76 usr  0.00 sys = 22.76 cpu)
     regex: 25 secs (24.88 usr  0.00 sys = 24.88 cpu)