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
              });

##</code><code>##

Benchmark: running match, silly, substr, unpack, each for at least 1 CPU seconds...
     match:  3 wallclock secs ( 1.00 usr +  0.02 sys =  1.02 CPU) @ 180382.35/s (n=183990)
     silly:  4 wallclock secs ( 1.15 usr +  0.09 sys =  1.24 CPU) @ 17341.13/s (n=21503)
    substr:  2 wallclock secs ( 1.00 usr +  0.05 sys =  1.05 CPU) @ 944029.52/s (n=991231)
    unpack:  2 wallclock secs ( 1.02 usr +  0.06 sys =  1.08 CPU) @ 362192.59/s (n=391168)