use Benchmark;
 
          $string = "hello world I am a string of some sort of length";
 
          timethese(-1, {
              "match" => sub { ($char) = $string =~ /^.{4}(.)/;},
              "unpack" => sub { ($char) = unpack("x4 A1", $string);},
              "substr" => sub { ($char) = substr($string,4,1);},
              "silly"  => sub { my $string2 = $string; $char = chop $string2 while length $string2 >= 4;}, #note the local
              });