print "The system is loading"; 
 
open (F,"test2.txt") || die "Cant"; 
@d=<F>; 
 
print "The system is complete loading";

print "The system is loading, please wait\n"; 
sleep(1);  
  
open (F,"test2.txt") or die "Cant open file  $!";  
@d=<F>;  
close F;  
 
print "The system is complete loading";

$| = 1; 
print "The system is loading, please wait\n";  
 
open (F,"test2.txt") or die "Cant open file  $!";   
@d=<F>;   
close F;   
  
print "The system is complete loading";

[root@fc4dev ~]# cat test.pl 
#!/usr/bin/perl 
 
use strict; 
use warnings; 
use Benchmark qw(cmpthese) ; 
 
my $file = 'data.txt'; 
 
cmpthese( -10, { 
        'while_file' => \&while_file, 
        'slurp_file'=> \&slurp_file 
}); 
 
 
sub while_file { 
   my $cnt; 
   open my $FH, $file or die $!; 
   while ( <$FH> ) { $cnt++ } 
   close $FH; 
} 
 
sub slurp_file { 
   my $cnt; 
   open my $FH, $file or die $!; 
   my @array = <$FH>; 
   $cnt++ for @array; 
   close $FH; 
}

[root@fc4dev ~]# ./test.pl 
           s/iter slurp_file while_file 
slurp_file   4.79         --       -82% 
while_file  0.838       471%         --