raku -e 'use Bench; my $b = Bench.new;  my $header = "Content-Length-Whatever: 5"; $b.cmpthese(500000, {regex => sub { $header ~~ m:i{"Content-Length-Whatever"}; }, chomplc => sub { $header.chomp.lc eq "content-length-whatever" }, lcregex => sub { $header.lc ~~ m{"content-length-whatever"}; } });'
Benchmark:
Timing 500000 iterations of chomplc, lcregex, regex...
   chomplc: 4.693 wallclock secs (4.032 usr 0.745 sys 4.776 cpu) @ 106545.676/s (n=500000)
   lcregex: 6.508 wallclock secs (5.807 usr 0.743 sys 6.550 cpu) @ 76823.230/s (n=500000)
     regex: 7.949 wallclock secs (7.216 usr 0.772 sys 7.987 cpu) @ 62904.895/s (n=500000)
O---------O----------O---------O---------O-------O
|         | Rate     | chomplc | lcregex | regex |
O=========O==========O=========O=========O=======O
| chomplc | 106546/s | --      | -91%    | -95%  |
| lcregex | 76823/s  | 993%    | --      | -42%  |
| regex   | 62905/s  | 1781%   | 72%     | --    |
O---------O----------O---------O---------O-------O