open(IN, "bigfile.txt");
while(<IN>){
  &big_sub1($_);
}
open(IN, "bigfile.txt");
while(<IN>){
  &big_sub2($_);
}

##</code><code>##

open(IN, "bigfile.txt");
while(<IN>){
  &big_sub1($_);
  &big_sub2($_);
}

##</code><code>##

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

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

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

##</code><code>##

sub1: 13 wallclock secs (12.80 CPU)
sub2:  8 wallclock secs (8.24 CPU)
sub3:  6 wallclock secs (6.66 CPU)