His code:

Benchmark: timing 5000000 iterations of sub1, sub2, sub3...
      sub1:  8 wallclock secs  @ 664805.21/s (n=5000000)
      sub2:  6 wallclock secs  @ 988924.05/s (n=5000000)
      sub3:  4 wallclock secs  @ 1139731.02/s (n=5000000)
[download]

Changed:

use Benchmark;

sub sub1(){
  my $val = 3;
  TTEST: {
    if($val == 1){last TTEST;}
    if($val == 2){last TTEST;}
    if($val == 3){last TTEST;}
    if($val == 4){last TTEST;}
  }
}

sub sub2(){
  my $val = 3;
  TTEST: {
    if($val == 1){last;}
    if($val == 2){last;}
    if($val == 3){last;}
    if($val == 4){last;}
  }
}

sub sub3(){
  my $val = 3;
  if($val == 1){}
  if($val == 2){}
  if($val == 3){}
  if($val == 4){}
}

my $codehash = {'sub1' => \&sub1,'sub2' => \&sub2,'sub3' => \&sub3};
timethese(5000000, $codehash);
[download]

Output:

Benchmark: timing 5000000 iterations of sub1, sub2, sub3...
      sub1:  8 wallclock secs ( 7.49 usr +  0.00 sys =  7.49 CPU) @ 66
+7467.63/s (n=5000000)
      sub2:  7 wallclock secs ( 7.27 usr + -0.01 sys =  7.26 CPU) @ 68
+8800.11/s (n=5000000)
      sub3:  5 wallclock secs ( 5.12 usr +  0.01 sys =  5.13 CPU) @ 97
+5419.43/s (n=5000000)
[download]